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A TREATISE ON THE PLAGUE AND YELLOW FEVER.

With an APPENDIX, containing

HISTORIES OF THE PLAGUE AT ATHENS IN THE TIME OF
THE PELOPONNESIAN WAR; AT CONSTANTINOPLE
IN THE TIME OF JUSTINIAN; AT LONDON IN
1665; AT MARSEILLES IN 1720; &c.

By JAMES TYTLER,

Compiler of the Medical Part of the Encyclopædia Britannica.

Let every one, Physician or not, freely declare his own sentiments about it;
let him assign any credible account of its rise, or the causes strong enough,
in his opinion, to introduce so terrible a scene.

Thucydides.

‘Twas all the business then
To tend the sick, and in their turns to die,
In heaps they fell.

Armstrong.

Published according to Act of Congress.

SALEM:

PRINTED BY JOSHUA CUSHING, FOR
B. B. MACANULTY.

CONTENTS.

A

TREATISE

ON THE

Plague and Yellow Fever.

PART FIRST.

Of the Asiatic or True Plague.

SECTION I.

Of the Plague in general.—Inquiry into the Antiquity of the Distemper.—Of the Plagues mentioned in the Old Testament.—History of several remarkable Plagues which, at various times, have desolated the world.

AMONG the many diseases which afflict the human race, we find ONE, upon record, so irresistible in its progress, so fatal in its attacks, and so entirely beyond the powers of medicine; that, like the serpent Python, the Leviathan, or the Mammoth, among animals, it has generally been distinguished by names expressive of its destroying nature; not, like other diseases, by any particular appellation derived from its symptoms. In the Hebrew language this distemper is expressed by the word which signifies perdition;[1] in Greek it is called loimos, from luo, to destroy; in Latin, pestis, from pessundo, to overthrow; and in English, the plague, from the Latin plaga, a stroke with a whip; alluding to the common opinion, that it is a scourge from heaven, taking vengeance on mankind for their sins.

Other distempers, called by the general name of Epidemics, have at different times infected whole cities, and even overspread extensive regions; but these, though sometimes very fatal, have always been found so much inferior to the distemper of which we treat, that, on a comparison, we may justly say, though epidemics have slain their thousands, the true plague has slain its ten thousands. In speaking of the destructive ravages of epidemics, we may count the dead by tens, by hundreds, or by thousands; but in the true plague, always by thousands, by myriads,[2] or by millions. Procopius, when speaking of a plague which desolated the world in his time, compares the number of the dead to the sand of the sea; and Mr. Gibbon, who attempts to specify, thinks they might amount to an hundred millions;[3] and I cannot help being of opinion, that the destruction generally occasioned by violent plagues, amounts to about one half of the population; the reasons for which opinion will be given in the course of this work. In all violent plagues, we hear of the dead being left unburied; of their being cast into pits, &c. But if we wish to make any gross comparison between the destructive power of the true plague, and that of any other violent epidemic, we cannot, perhaps, have a better instance than that which took place at Bassorah (a city on the confines of Persia) in the years 1773 and 1780.[4] In the former of these years that city was visited by the true plague; and in the latter, by an epidemic remittent fever. The fever was most violent in its kind, and destroyed twenty-five thousand in the city and neighbourhood; but the true plague, no fewer than two hundred and seventy-five thousand in the same place. Supposing the two computations therefore to be equally exact, we must calculate this plague to have been eleven times more deadly than the epidemic. If therefore the ingenious classifiers, in modern times, have brought into alliance the plague with other epidemic diseases, and characterised the former from the latter; we may justly say, that they have fallen into the same error with other naturalists, who characterise the superior from the inferior; the lion from the cat, not the cat from the lion. As to the remedies applied in these diseases, doubtful in epidemics, they so universally fail in the true plague, that, notwithstanding the improved state of medicine, we may yet say, it stands among diseases, in a great measure, like a giant without any champion to oppose; like a poison without any antidote.

In this unhappy predicament, the breaking out of a plague, in any city or country, proves a most distressing calamity, not only on account of the numbers destroyed by the disease itself, but by reason of the bonds of society being loosed; so that humanity gives way to terror; children are abandoned by their parents, and parents by their children; every thing wears the appearance of ruin and desolation; while, in too many instances, avarice urges on the unprincipled to rapine, or even to murder. Nor are the cruel modes of prevention, sometimes practiced even by the authority of the magistrate, less abhorrent to humanity, then the lawless outrages of the thief or murderer. Instances of all this will appear in the course of the work; the following are so remarkable, that I cannot help inserting them in this place. In the great plague at Marseilles, in 1720, the town being almost deserted, and few choosing to venture into it, “three sea-captains, and some hundreds of sailors, having the courage to enter the city, from the sea-side, found therein a gang of murderers, who made it their business to destroy people seized with the plague, and to plunder their houses. The ringleader of them, named Rouanne, a gunsmith, was broken alive upon the wheel, and forty others were hanged. Rouanne owned that he had killed a thousand persons. There were found, upon one of the murderers, jewels to the value of more than thirty thousand livres.”[5] During the time of this public calamity, four men, who came from Marseilles to Aix, were shot by order of the parliament, lest they should have brought the infection along with them.[6] Even this is not equal to what Mr. Howard informs us was practiced in a hamlet of Dalmatia, where, the plague having raged with such violence, that only two or three remained; the neighbouring magistrates ordered these miserable survivors to be shot. At such prices will people buy a precarious, nay, an imaginary, safety. In short, what Mr. Gibbon says of the situation of people in the time of violent earthquakes, will also, in a great measure, hold good in the time of pestilence, or any great public calamity. “Instead of the mutual sympathy which might comfort and assist the distressed, they dreadfully experience the vices and passions which are released from a fear of punishment; the houses are pillaged by intrepid avarice, revenge embraces the moment and selects the victim: while [7]vengeance frequently overtakes the assassin or ravisher in the consummation of his crimes.”

Whether the world hath been in the same predicament ever since the human race began to multiply, or whether plagues have originated at some remote period, is a question not easily determined. It is certain that, as far as histories go, they give us accounts of plagues; much less frequent indeed in very ancient times than in those which followed; but the compass of historical knowledge is narrow. There are no authentic histories of any nation previous to the termination of those of the Old Testament. Where sacred history ends, profane history begins. The fabulous period affords many accounts of wars, heroes, giants, and monsters, but scarce any of plagues. Diodorus Siculus indeed makes mention of a plague which happened in Greece, after the flood of Deucalion; and which, he says, was occasioned by the general corruption of vegetables, &c. consequent on the flood. Deucalion’s flood is supposed to have been nearly cotemporary with the departure of the Israelites from Egypt; so that, if there is any truth in the relation of Diodorus, it is not improbable that some of the Egyptian plagues might have spread into Greece. We are likewise told of a pestilence at Athens in the time of Theseus;[8] but all the accounts of these times are so uncertain, and so much involved in fable, that little or no dependence can be placed on any of them.

The first distinct account we have of plagues of any kind, then, is in the book of Exodus, where we are told of many heavy judgments sent upon the Egyptians because of their disobedience. Before this, indeed, we read of plagues sent on the king of Egypt, for having taken Abraham’s wife; but as these fell only upon the king and his household, we cannot suppose any thing like a general pestilence to have taken place among the people. In like manner did it happen to Abimelech, king of Gerar, on the same account. All the women belonging to the king’s household were rendered barren for a time; but we hear of nothing happening to the nation at large. Again, when Moses and Aaron went in before Pharaoh, they said to him, “Let us go and sacrifice to the Lord our God; lest he fall upon us with the sword, or with pestilence.” This shews indeed that both Moses and Pharaoh knew that such a thing as pestilence existed, or might exist; but it cannot prove that the disease we now call the plague or pestilence commonly took place among nations in those days as it has done since. Even among the plagues inflicted upon the Egyptians by the hand of Moses and Aaron, we find only two that can be supposed to have any similarity to the disease we now call the plague; viz. the boil, and the destruction of their first born. The former may have been pestilential buboes; the latter also may have been the effect of a most malignant pestilence; such as, in the beginning of it, is said frequently to kill suddenly, as by lightning; but whether it was so or not, we cannot now determine.

In the history of Job, who is supposed to have been cotemporary with Moses, we have a case more in point. The boils, with which he was covered, are by Dr. Mead supposed to have been the small pox; though in the true plague the body is sometimes covered with gangrenous pustules, constituting a disease still more dangerous and painful than the small pox; but whatever the disease of Job was, we may reasonably conclude, that in his time there was none similar to it commonly existing among mankind.

After the departure of the Israelites from Egypt, we find frequent mention of a plague as a disease commonly to be met with; but it was always that of leprosy; those destructive plagues, which might be supposed to resemble the disease we now call by that name, being all miraculous. Concerning the prevalence of the leprosy among the Jews, Diodorus says that they “were driven out of Egypt as impious, and hateful to the gods; for their bodies being overspread and infected with the itch and leprosy, (by way of expiation) they got them together, and, as profane and wicked wretches, expelled them out of their coasts.” This he tells us was a reason given to one of the kings of Syria why he should exterminate the Jews. In another place our author gives the following account of the origin of the Jewish nation. “In ancient times there happened a great plague in Egypt, and many ascribed the cause of it to God, who was offended with them. For there being multitudes of strangers of several nations who inhabited there, who used foreign ceremonies, the ancient manner of worship was quite lost and forgotten. Hence the natural inhabitants concluded, that unless the strangers were driven out, they should never be freed from their miseries. Upon which they were all expelled,” &c. He then tells us that some of them came into Greece under the conduct of Danaus and Cadmus; but the greater part entered Judea, then quite desert and uninhabited. Their leader “was one Moses, a very wise and valiant man,” &c.[9]

The allusion, in this last passage of Diodorus, to the plagues of Egypt, mentioned in Exodus, is manifest; and it is equally manifest, that the Egyptians themselves, as well as the sacred historian, owned them to be miraculous. Here, however, let it be remarked, that, though these, and others inflicted on the Israelites, were miraculous, we are not from thence to conclude that they took place without the intervention of natural causes. On the contrary, in speaking of the plagues of Egypt, we are told, that when the locusts came, “the Lord sent a strong east wind, all that day and all that night; and when it was morning, the east wind brought the locusts.” In like manner “the Lord turned a mighty strong west wind, which took away the locusts, and cast them into the Red sea.” Again, when the sea itself was divided, “the Lord caused it to go back by a strong east wind all that night.” The Egyptians were witnesses to this; but, as they did not believe that the powers of nature had any superior, they could never be induced to think that any of the elements would take part in a dispute between two nations, or favour the one more than the other.

In diseases inflicted on the human body, we are assured that the powers of nature were as much employed as in the miracles already mentioned. When it was told David that the child born to him by Bathsheba should die, the infant was seized with a natural distemper, probably a fever, and died the seventh day. When Hezekiah was informed that he should die, he did not, any more than David had done, give himself up to despair; but used, for his recovery, such means as were in his power, viz. prayers to God; from whom, by the constitution of things under the Old Testament, he would receive a direct answer. And it is remarkable, that though the answer was favourable, yet the disease was not removed by any invisible power operating like a charm, but by the use of a remedy. It is plain therefore that this disease was occasioned by one natural power, and removed by another. The boil (for that was the distemper) was brought to maturity by a poultice of figs, and the king recovered.[10] If then the scripture informs us, that even where the Deity himself speaks, he has directed the use of a remedy, much more ought we to be diligent in the use of such as our feeble skill can suggest, in those cases where he leaves us entirely to the exercise of our own judgments. To sit down supinely, in case of a dangerous distemper, with a notion, that if God wills us to die we certainly shall die, in any use of natural means; and if he wills the contrary, that we shall as certainly recover, in any neglect of them; is a conduct equally unscriptural and absurd.

In the books of Moses we find the Israelites, in case of disobedience, threatened with the botch of Egypt; with terror, consumption, and the burning ague. From the name of this last we may reasonably suppose it to have been the same with the remitting fever of the East, which is attended with the most intolerable sensation of burning in the bowels; but whatever the nature of these diseases might have been, they certainly were not very common in the world at that time, or they would not have been threatened as extraordinary judgments. They were not the same with the pestilence; because we find, that after they had been threatened with fever, consumption, and extreme burning, it is added, “I will make the pestilence cleave unto thee:” as if it had been said, that the pestilence, which hitherto had appeared only on extraordinary occasions, should then become endemic, and never leave them. But, on the whole, the first account we have of any general plague, seems to be that which was inflicted on the Jews on account of the sin of their king in numbering the people. David was nearly cotemporary with the Trojan war; and Homer, in the first book of his Iliad, informs us, that a plague likewise took place in the camp of the Greeks; and that too for the sin of their king in carrying off the daughter of the priest of Apollo, and refusing to restore her at the entreaty of her father.

In comparing the account of the sacred historian with that given by Homer, we cannot help observing a striking similarity between them. Both plagues were inflicted on the people for the sin of their kings; both were miraculous; the one continued three days, the other nine. In both the Deity himself appeared: an angel brandished a drawn sword over Jerusalem; and Homer says, that, from the top of Olympus, Apollo shot his arrows into the Grecian camp. Lastly, both were stopped in a similar manner: David offered sacrifices to the true God; and Agamemnon returned Chryseis, his captive, to her father, the priest of Apollo, by whose prayers and sacrifices the plague was stopped. Hence it seems not impossible, that the story told by Homer, is only that of David, altered as he thought most proper for embellishing his poem; and that this was the first remarkable plague in the world.

In the year 767 B. C. we hear of a universal pestilence; but the imperfect state of history in those early periods affords few accounts that can be depended upon, either concerning that or any thing else.[11] Till after the foundation of Rome, indeed, authentic history scarce commences; and it is not till the 279th year of that city, that we hear of its being in any remarkable degree infected with a pestilential disorder.[12] The plague we speak of is said to have taken place about the year 469 B. C. which comes within 38 years of that of Athens in the time of the Peloponnesian war. The near coincidence of these dates, in times so remote, and when chronology was so little settled, tends to excite a suspicion that both arose from the same infection. Of its ravages at Athens we have an excellent account by the historian Thucydides,[13] who was an eye witness of what he writes. He says, that according to report it began in Ethiopia, from whence it came down into Egypt, and thence into other countries. It is possible, therefore, that it might reach Italy some time before it came into Greece; for it seems scarce probable, that such a very violent infection could have taken place in Italy without being communicated to the neighbouring countries; whence we may reasonably conclude, that the first plague at Rome, and that of Thucydides, were the same. At Rome, we are informed, it swept away almost all the flower of the youth who were able to bear arms, the greatest part of the tribunes, and both the consuls. The mortality was so great, that no place of sepulture could be found for the dead bodies, but they were thrown promiscuously into the Tiber. In short, so low were the Romans at this time reduced, that the Æqui and Volsci, two Italian nations with whom they were almost always at war, made an immediate attack, in hopes of being easily able to carry the city; but in this they were disappointed. The situation of Athens was truly deplorable; being not only engaged in a foreign war, but crowded with people from the country; numbers dying daily in the streets, and the survivors giving themselves up to all manner of licentiousness.[14]

As it seems probable that the same infection desolated both Rome and Athens, so it seems not unlikely that it was a continuance of the same which destroyed the Carthaginian army in Sicily, while carrying on a successful war against Dionysius, tyrant of Syracuse. The plague, as we are informed by the Universal History, was common in the Carthaginian territories, especially those on the continent of Africa; and this pestilence broke out soon after the conclusion of the Peloponnesian war. As it originally came from Africa, it is probable that it had never been quite extinguished there; and the compilers of the Universal History think it probable that the army might have brought the seeds of it along with them into Sicily. But, whatever was the origin, the distemper soon became so malignant, that the living were not sufficient to bury the dead; and those who attended the sick perished in such a manner, that, after some time, few dared to come near them. At first they gave the dead a kind of burial; but in time the number became so great, and the survivors so few and weak, that an hundred and fifty thousand are said to have rotted above ground. “Justin seems to intimate that almost the whole Carthaginian army perished by the plague; and that in a manner all at once, as it were in an instant. Diodorus, however, informs us, that a considerable body of Africans and Iberians survived the dreadful calamity. It is worth observation, that not a single person of those who attended the sick survived.” The miserable remains of this army, consisting at first of more than three hundred thousand, were now attacked by their enemies, whom they were no longer able to resist. Their land forces were entirely defeated, and their fleet was burnt: “the Gods themselves, (says Diodorus) when the ships were all in a blaze, and the flames ascending above the masts, seeming to destroy the Carthaginians with lightning from heaven.” Forty gallies still remained, and the unfortunate general was now obliged to purchase liberty to return with the few men he had left. But even these were treacherously attacked by the tyrant’s fleet, and several of them sunk. On his arrival at Carthage, he found the whole city not only in mourning, but in despair: “the wretched inhabitants giving full vent to their grief, made the shore ring with their groans and lamentations. In short, a greater scene of horror, except the spot of ground where the Carthaginian army encamped before Syracuse, than Carthage now was, cannot well be conceived.” This reception completed the despair of the unhappy general. Clothing himself in mean and sordid attire, he joined with the rest in bewailing their common calamities. After some desperate exclamations against the gods, whom he accused of partiality, “The enemy, said he, may rejoice at our misery, but have no reason to glory in it. The troops we have lost did not fall by their valour, nor did they now oblige those that arrived here to leave Sicily by force. We return victorious over the Syracusians, and are only defeated by the plague. As for the baggage found in our camp, this ought not to be looked upon as the spoils of a conquered enemy, but as moveables which the casual death of their owners has left the Syracusians in possession of.” Having then gone on to express his grief for the loss of his army, and declared his intention not to outlive them, he shut himself up in his house, refusing admittance even to his own children, and put an end to his life.[15]

Whether the unfortunate remains of this army brought with them the infection to Carthage, and there produced a new scene of desolation, we are not informed; but there seems to have been a very great tendency to pestilential disorders in the Carthaginian armies; for, in the time of the siege of Syracuse by Marcellus, a plague broke out in the camp of the Carthaginians who had come to assist the Syracusians. From them it passed into the city itself, with so much malignity, that nothing was to be seen but heaps of dead and dying. None durst receive or assist the sick, for fear of being infected by them; and the bodies of the dead were, for the same reason, left unburied, to infect and poison the air with their putridity and corruption. Nothing was heard, night and day, but groans of dying men; and the heaps of dead bodies continually presented mournful objects to the living, who expected every moment the same fate.[16] The infection reached the Roman camp; but we do not hear of its being conveyed, at this time, either to Rome or Carthage. In the time of the contest with Jugurtha, however, a very terrible calamity took place in Africa. “According to Orosius, a great part of Africa was covered with locusts, which destroyed all the produce of the earth, and even devoured dry wood. But, at last, they were all carried by the wind into the sea, out of which being thrown in vast heaps upon the shore, a plague ensued, which swept away an infinite number of animals of all kinds. In Numidia only, perished eight hundred thousand men; and in Africa Propria, two hundred thousand; among the rest, thirty thousand Roman soldiers, quartered in and about Utica for the defence of the last mentioned province. At Utica, in particular, the plague raged with such violence, that fifteen hundred dead bodies were carried out of one gate in a day.”[17]

From the time that the Romans finished their African wars, till they had accomplished most of their conquests in Asia, their empire seems to have continued free from this dreadful scourge; but soon after the destruction of Jerusalem by Titus, such a violent infection seized on the city, that for some time upwards of twenty thousand are said to have died in it daily.

As the Roman arms were carried still farther to the eastward, and all the countries reduced, to the confines of Persia, the plague seems to have become more common among them. In the time of Marcus Aurelius, a war was undertaken against the Parthians, which was carried on by the Romans with great success, and with no less cruelty; for, though the city of Seleucia opened its gates to the Roman general, he caused the inhabitants, to the number of four hundred thousand, to be massacred. But they soon paid dear for this cruelty, by a dreadful pestilence, which broke out, according to the historian Ammianus Marcellinus, in the very city which they had desolated, and was brought by their army into Italy, from whence it spread throughout the whole empire. Other historians say, that it originated in Ethiopia, from whence it spread into Egypt, and thence into the country of the Parthians. We know not how long the infection continued; only that, some years afterwards, when the emperor was defeated by the Germans, the pestilence still raged to such a degree, that slaves, gladiators, and even the banditti of Dalmatia and Dardania, were enlisted for the defence of the empire. It is certain that great havock must have been made by it, as we find that the barbarians were encouraged to invade the empire on all sides, and could scarcely be repulsed; insomuch that historians compare this with the most destructive wars the Romans had ever waged.[18]

During the time that the empire was overrun by the northern barbarians, the plague frequently made its appearance; which we shall have occasion to notice more particularly in the following section; but in those times the destruction by the sword was so extraordinary, that less mention is made by history of any pestilential disorder. In the time of Justinian, however, about sixty-five years after the final destruction of the western empire, the most violent plague recorded in history took place. Of this we have a particular account by Procopius.[19] “The distemper (says Mr. Gibbon) arose in the neighbourhood of Pelusium, on the confines of Egypt, between the Sarbonian bog and the eastern channel of the Nile. From thence, tracing, as it were, a double path, it spread to the east, over Syria, Persia, and the Indies, and penetrated to the west, along the coast of Africa, and over the continent of Europe. In the spring of the second year, Constantinople, during three or four months, was visited by this pestilence. Such was the corruption of the air, that the pestilence was not checked, nor alleviated, by any difference of seasons. The numbers that perished in this extraordinary mortality have not been recorded; only we find that, during three months, there died at Constantinople five, and at last ten thousand a day. Many cities of the east were left vacant, and, in several districts of Italy, the harvest and vintage withered on the ground. The triple scourge of war, pestilence and famine afflicted the subjects of Justinian; and his reign is disgraced by a visible decrease of the human species, which has never been repaired, in some of the fairest countries of the globe.”[20]

This plague broke out in the time of Justinian, in the year 541 or 542 of the christian era; and not only ravaged Constantinople in the time of Justinian, but returned with increased violence during the reigns of many of his successors. In the time of Mauritius we find the Avari, a barbarous nation to the north of the Danube, driven back by the plague after they had crossed that river to invade the Roman territories. The reign of Phocas, successor to Mauritius, was still more unfortunate. “Great numbers were swept off, either by famine or pestilence; the earth refused her fruits in season; the winters were so severe, that the seas were frozen, and the fish destroyed.” Phocas ascended the imperial throne in 603; but in the midst of such confusion as then filled the world, we can scarce expect an accurate account of the time when this most malignant pestilence ceased. We can scarcely suppose it to have lasted two centuries; but, in the reign of Constantine Copronymus, which began in 742, we find the distemper still raging, and the same dreadful phenomena of nature still continuing. The plague, we are now told, broke out in Calabria in Italy; whence it soon spread over Greece, Sicily, the islands in the Ægean sea; and at last reached Constantinople; where it raged for three years together, with such fury, that the living were scarce sufficient to bury the dead. The earthquakes, which accompanied or preceded this pestilence, were such as had never been known in any age. In Syria and Palestine several cities were swallowed up; others, entirely ruined; and some, if we may give credit to Nicephorus, removed without any considerable damage, six miles and upwards from their former seats. At the same time happened an extraordinary darkness, which lasted from the fourth of August to the first of October, there being little or no distinction, during all that time, between day and night.[21] During the reign of the same prince, there happened such an extraordinary frost, that, at Constantinople, both seas were frozen for an hundred miles from the shore; the ice being covered with snow twenty cubits deep, and sufficiently strong to bear the heaviest carriages. When the frost broke, mountains of ice and frozen snow, being driven by the wind through the straits, did a great deal of damage to the walls of Constantinople. The month following, several prodigies appeared, or were thought to appear, in the air. At the same time a comet, which the Greeks called Docites, because it resembled a beam, was seen for ten days in the east, from whence it moved into the west, and shone there for one and twenty days more. The people were struck with terror and amazement at the sight of the prodigies, and apprehended the last day to be at hand.[22] Dreadful earthquakes, strange phenomena in the heavens, inundations, &c. occurred in the year 812, during the reign of Michael Balbus; but no remarkable plague is mentioned by the Greek historians, till the year 1025, when a new train of calamities took place. The plague broke out in Cappadocia, raging with such violence there, as well as in Paphlagonia and Armenia, that the people were forced to abandon their dwellings. A terrible famine followed; after which the earthquakes again commenced with redoubled fury: at Constantinople they continued forty days together; while people were terrified by a comet (probably a large meteor) which passed with a dreadful noise from north to south; the whole horizon appearing to be in a flame.

From these calamities the world, at least that part of it known to the Greek historians, appears to have enjoyed some respite till the year 1346. Indeed we may now say, as in the time of the invasion by the northern barbarians, that the sword, and not the pestilence, was the plague of those times. A most violent and universal pestilence, however, now took place; though, for want of such historians as Thucydides and Procopius, we cannot here give a particular account of it. In general we are told, that it began in the kingdom of Cathay (the northern part of China) from whence it gradually overspread all the countries between that and the western extremity of Asia. Invading, at last, Constantinople, it proceeded from thence to Greece, Italy, France, Africa, Germany, Hungary, Denmark, Britain and Ireland. Thus, it seems to have been as extensive a contagion as ever appeared in the world. It is even probable, that, from the remains of this contagion, Europe hath been but very lately set at liberty; as we hear, not long after, of plagues being very frequent in different parts of that continent. In England it assumed somewhat of a new form towards the end of the fifteenth century; being then known by the name of the English Sweating Sickness. But, except in the greater propensity to sweat, the disease appears not to have differed from the true plague. The sweating sickness first made its appearance in the army of Henry VII, when he landed at Milford in 1483; and that year invaded London, where it continued only from the 21st of September to the end of October. It returned in 1485, 1506, 1517, 1528 and 1551; since which time it has not been known in Britain. In 1517 it was extremely violent and mortal; sometimes killing the sick in three hours; and so general was the infection, that, in some places, one half of the inhabitants died. In 1528 it also raged with great violence; the sick sometimes dying in four hours. The last attack, in 1551, was also very violent. In 1529 it appeared in Holland and Germany, destroying great numbers of people; but it hath not been observed, at least in any remarkable degree, in those countries since that time. In the course of the 17th century, various parts of Europe have suffered very much from the plague in its usual form. Indeed (for reasons given in the subsequent section) we can scarce suppose the pestilential contagion ever to have ceased entirely. In 1603, London was visited with the plague; and on this occasion the practice of shutting up infected houses was first introduced.[23] In 1656 another plague took place in the same metropolis, but does not appear to have made any violent attack. In Naples it raged that year with great fury; destroying, according to some accounts, fifteen thousand, according to others, twenty thousand, a day. But these accounts the author of the Journal just quoted, with great probability, supposes to have been exaggerated. Others say, that four hundred thousand Neapolitans were destroyed by this infection; so that we must at any rate believe it to have been very violent. In the plague of London in 1665, immense numbers perished; and particular accounts were published of this calamity; of which an abridgment is given in the Appendix to this work, No. III. Since that time it has not been known in Britain; but other parts of Europe have not been equally fortunate. In the beginning of the eighteenth century it appeared in several parts of the continent; particularly in Copenhagen in the year 1711; where it committed great ravages, as it had done at Dantzic two years before; but in 1720 it appeared at Marseilles in France, where it raged with such fury as to destroy sixty out of the hundred thousand supposed to be the whole population of the place.[24] Since that time France hath been free from the distemper; but in Sicily, the dominions of the Ottoman Porte, and places adjacent, it hath been felt very severely. In 1743 it was supposed to have destroyed two thirds of the inhabitants of Messina. A particular account of its ravages was read before the Royal Society of London by Dr. Mead. The following is taken from Dr. Lobb’s Treatise on the Plague. “From the beginning of June to the end of July, of forty thousand inhabitants, two thirds perished. The disorders in the city were incredible. All the bakers died, and no bread was baked for many days. The streets were full of dead bodies; at one time from twelve to fifteen thousand remaining in the open air: men, women and children, rich and poor, all together dragged to the church doors. The vaults being full, and the living not sufficient to carry the dead out of the city, they were obliged to put them on funeral piles, and burn them promiscuously. Nothing was more shocking than to see people, far above the common stations, go about begging for a loaf of bread, when they could hardly walk, with their tumours upon them; and few were in a state to help them. All these calamities did not hinder the most execrable villanies, which were committed every moment; and, though so few survived, the governor was obliged to make several public examples.”

In the Turkish dominions, though we have not read of such extraordinary devastations as formerly took place, yet we are assured that the pestilence rages there very frequently. From 1756 to 1762 we have histories of it by Dr. Russel and others, the substance of which accounts is given in the Appendix, No. V. In the time of the great war between the Turks and Russians, it found its way to Moscow, which city it invaded in 1771. M. Savary says, it was brought thither by infected merchandise from the store houses of the Jews; and that it carried off two hundred thousand people. In the sixth volume of the Medical Commentaries, however, we are told that it was brought from the army by two soldiers; both of whom were carried into the military hospital, and both died. The anatomist who dissected their bodies died also. The infection quickly seized the hospital, and thence the whole city. This happening in the beginning of the year, its progress was for some time checked by the cold; but its ravages became greater as the summer advanced. It raged most violently during the months of July, August and September; in which time there were instances of its destroying twelve hundred persons in a day. Twenty-five thousand died in the month of September; in the course of which month scarce one in an hundred of the infected recovered. Only seventy thousand, according to this account, perished by the disease. The year 1773 proved very fatal to Bassorah; where, as formerly mentioned, two hundred and seventy-five thousand perished in the summer season, through the violence of the distemper.[25] But in countries where the plague rages so frequently, and where there are few that make observations with any accuracy, we cannot expect complete histories of every attack made by it; neither would the limits of this Treatise admit of a detail of them, though there were. We know, however, that since the year we speak of, the plague has ravaged Dalmatia, particularly in the year 1784, when it almost desolated the town of Spalatro, destroying three or four thousand of its inhabitants. Though some countries therefore have for a number of years remained free from the attacks of this terrible enemy, yet there are others where it is as it were stored up, and from whence it may, on a proper occasion, break forth as formerly, and once more spread ruin and desolation through the world.

SECTION II.

Of the Countries where the Plague is supposed to originate.—The Influence of Climate in producing Diseases—And of the Moral Conduct of the Human Race in producing and influencing the same.

IN considering the origin of a calamity so dreadful and so universal, we might reasonably suppose that the fatal spots which gave rise to it would long ago have been marked out and abandoned by the human race altogether. But this is far from being the case. In the accounts already given of various plagues, they are always said to have been imported from country to country, but never to have originated in that of the person who wrote of them. If a plague arose in Greece, we are told it came from Egypt; if in Egypt, it came from Ethiopia; and had we any Ethiopic historians, they would no doubt have told us that it came from the land of the Hottentots, from Terra Australis Incognita, or some other country as far distant as possible from their own. In short, though it has been a most generally received opinion, that plagues are the immediate effects of the displeasure of the Deity on account of the sins of men; yet, except David and Homer (already quoted) we find not one who has had the candour to acknowledge that a plague originated among his countrymen on account of their sins in particular. In former times Egypt and Ethiopia were marked out as the two great sources of the plague; and even as late as the writings of Dr. Mead we find that the same opinion prevailed. The Doctor, who attempts to explain the causes of the plague, derives it entirely from the filth of the city of Cairo, particularly of the canal that runs through it. But later writers, who have visited and resided in Egypt, assure us that the country is extremely healthy, and that the plague is always brought there from Constantinople. It is true that Dr. Timone, in the Philosophical Transactions, No. 364, tells us, that it appears from daily observation, as well as from history, that the plague comes to Constantinople from Egypt; but the united testimonies of Savary, Volney, Mariti and Russel, who all agree that Egypt receives the infection from Constantinople, must undoubtedly preponderate.

“The pestilence (says M. Savary) is not a native of Egypt. I have collected information from the Egyptians, and foreign physicians who have lived there twenty or thirty years; which all tended to prove the contrary. They have assured me that this epidemic disease was brought thither by the Turks, though it has committed great ravages. I myself saw the caravelles of the Grand Signior, in 1778, unlade, according to custom, the silks of Syria at Damietta. The plague is almost always on board; and they landed, without opposition, their merchandise, and their people who had the plague. It was the month of August; and, as the disease was then over in Egypt, it did not communicate that season. The vessels set sail, and went to poison other places. The summer following, the ships of Constantinople, alike infected, came to the port of Alexandria, where they landed their diseased without injury to the inhabitants. It is an observation of ages, that if, during the months of June, July and August, infected merchandise be brought into Egypt, the plague expires of itself, and the people have no fears; and if brought at other seasons, and communicated, it then ceases. A proof that it is not a native of Egypt is, that, except in times of great famine, it never breaks out in Grand Cairo, nor the inland towns, but always begins at the seaports on the arrival of Turkish vessels, and travels to the capital; whence it proceeds as far as Syria. Having come to a period in Cairo, and being again introduced by the people of Upper Egypt, it renews with greater fury, and sometimes sweeps off two or three hundred thousand souls; but always stops in the month of June, or those who catch it then are easily cured. Smyrna and Constantinople are now the residence of this most dreadful affliction.”

M. Volney informs us, that the European merchants residing at Alexandria agree in declaring that the disease never proceeds from the internal parts of the country, but always makes its first appearance on the sea-coasts at Alexandria; from thence it passes to Rosetta, from Rosetta to Cairo, and from Cairo to Damietta, and through the rest of the Delta. It is invariably preceded by the arrival of some vessel from Smyrna or Constantinople; and it is observed, that if the plague has been violent during the summer, the danger is greater for the Alexandrians during the following winter.

To the same purpose, the Abbe Mariti says, “The plague does not usually reside in Syria, nor is this the place where it usually begins. It receives this fatal present from Egypt, where its usual seat is Alexandria, Cairo or Damietta. The plague of 1760 came at once from Cairo and Alexandria; to the latter of which it had been brought from Constantinople. When it comes from that capital, as well as from the cities of Smyrna and Salonica, it acquires a peculiar malignity; and its activity never expands itself with more fury than in the plains of Egypt, which it overspreads with incredible rapidity. It is observed, that this plague, so destructive to Egypt, seldom attacks Syria; but that the latter has every thing to dread from a plague hatched in the bosom of Egypt.”

The testimony of these three authors, who have all been lately on the spot, must certainly have very great weight, especially when corroborated by that of Dr. Russel; for which see Appendix, No. V. But still there is some difficulty. M. Savary informs us, that, except in cases of great famine, the disease never breaks out in Cairo; which certainly implies that in cases of famine it does originate in the city itself; and Mariti, by saying that the Syrians have much reason to dread a plague hatched in the bosom of Egypt, undoubtedly intimates that plagues sometimes do originate in Egypt. Smyrna and Salonica likewise seem to come in for their share of the blame; and Dr. McBride, in his Practice of Physic, informs us, that some parts of Turky are visited by the plague once in six or seven years; and M. Savary says, that Egypt is visited with it once in four or five years; but if Egypt never receives it but from Turky, it would seem that the plague could at least be no more frequent than in that country; or, if the fact be otherwise, that the disease must either originate in Egypt itself, or be brought to it from some other country than Turky. Dr. Timone, in the paper already quoted,[26] tells us, that the plague has taken up its residence in Constantinople; but that, though the seeds of the old plague are scarce ever wanting, yet a new infection is likewise imported from time to time. Thus, in attempting to find out the countries where the plague originates, we are led in a circle. Constantinople accuses Egypt, and Egypt recriminates on Constantinople. Ethiopia, the most distant and least known of those countries which in former times had any connexion with the more civilized parts of the world, for a long time bore the blame of all; but the Jesuit missionaries who resided long in Abyssinia (the ancient Ethiopia) do not mention the plague as more common in that country than some others; neither does Mr. Bruce, in the accounts he has published, take notice of any such thing. Ethiopia could not speak for itself, by reason of the ignorance and barbarity of its inhabitants; and Constantinople is now very much in the same predicament. The investigation of this subject therefore would require an accurate account of the climates of those countries where the plague is found to commit the greatest ravages, and a comparison of them with those which are now accounted the most unhealthy in other respects, and likewise a comparison of the diseases produced in the latter, with the true plague.

The most unhealthy climates now existing (those where the plague commonly rages excepted) are to be met with in the hottest parts of the world; the East and West Indies, the wastes of Africa, and some parts of America. In all these, Dr. Lind, who has written a treatise on the diseases incident to Europeans in hot climates, seems to lay the whole blame upon the heat and moisture accompanying it. In the East Indies Bencoolen, in the island of Sumatra, is the most unhealthy of all the English settlements; but he informs us, that by building their fort on a dry, elevated place, about three miles from the town, it became sufficiently healthy. Next to this, Bengal is most subject to sickness; for which he assigns the following reason: “The rainy season commences at Bengal in June, and continues till October; the remainder of the year is healthy and pleasant. During the rains, this rich and fertile country is covered by the Ganges, and converted as it were into a large pool of water. In the month of October, when the stagnated water begins to be exhaled by the heat of the sun, the air is then greatly polluted by the vapours from the slime and mud left by the Ganges, and by the corruption of dead fish and other animals. Diseases then rage, attacking chiefly such as are lately arrived. The distempers are fevers of the remitting or intermitting kind; for, though sometimes they may continue several days without sensible remission, yet they have in general a great tendency to it. If the season be very sickly, some are seized with a malignant fever, of which they soon die. The body is covered with blotches of a livid colour, and the corpse, in a few hours, turns quite livid and corrupted. At this time fluxes prevail, which may be called bilious or putrid, the better to distinguish them from others which are accompanied with inflammation of the bowels. The island of Bombay has of late been rendered much more healthy than it formerly was, by a wall built to prevent the encroachments of the sea, where it formed a salt marsh; and by an order that none of the natives should manure their cocoa-trees with putrid fish.

“Batavia, the capital of the Dutch East India dominions, is annually subject to a fatal and consuming sickness. Here the Dutch, in attempting to make this, their capital in India, resemble their cities in Europe, have adorned it with canals or ditches, intersecting each other, running through every part of it. Notwithstanding the utmost care to keep these clean, during the rainy season, and after it, they become extremely noxious to the inhabitants, but especially to strangers. It has been remarked, that the sickness rages with the greatest violence when the rains have abated, and the sun has evaporated the water in the ditches, so that the mud begins to appear. This happened in 1764, when some British ships of war had occasion to stay for a little time at Batavia. The stench from the mud was intolerable; the fever was of the remitting kind; some were suddenly seized with a delirium, and died in the first fit; but none survived the attack of a third. Nor was the sickness at that time confined to the ships; the whole city afforded a scene of disease and death; streets covered with funerals, bells tolling from morning to night, and horses jaded with dragging the dead in herses to their graves. At that time a slight cut of the skin, the least scratch of a nail, or the most inconsiderable wound, turned quickly into a putrid, spreading ulcer, which, in twenty-four hours, consumed the flesh, even to the bone. Besides these malignant and remitting fevers, which rage during the wet season in the unhealthy parts of the East Indies, Europeans, especially such as live intemperately, are also subject to fluxes, and to an inflammation, or disease of the liver; which last is almost peculiar to India, and particularly to the Coromandel coast.”

In the same work we have an extract from Mr. Ives’s journal of a journey from India to Europe by land. “Gambroon in Persia, says he, is very unhealthful. Few Europeans escape being seized with putrid intermitting fevers, which rage from May to September, and are often followed with obstructions of the liver. Various authors who have treated of Gambroon, do, as well as the present English factory, impute its unhealthfulness, during the summer months, to the noxious effluvia with which the air is contaminated, from the great quantities of blubber fish left by the sea upon the shore, and which very soon become highly offensive. In the rainy seasons, at the island of Karee, in the Persian Gulf, intermitting fevers and fluxes are the usual distempers. On our arrival at Bagdad (supposed to contain 500,000 souls) we found a purple fever raging in the city; but though it was computed that an eighth part of the inhabitants were ill, yet the distemper was far from being mortal. Here we were informed that the Arabs had broken down the banks of the river near Bassorah, with a design to cover with water the deserts in its neighbourhood. This, it seems, is the usual method of revenge taken by the Arabs for any injury done them by the Turks at Bassorah; and was represented to us as an act of the most shocking barbarity, since a general consuming sickness would undoubtedly be the consequence. This was the case fifteen years before, when the Arabs, by demolishing the banks of this river, laid the environs of Bassorah under water. The stagnating and putrefying water in the adjacent country, and the great quantity of dead and corrupted fish at that time lying upon the shore, polluted the whole atmosphere, and produced a putrid and most mortal fever, of which between twelve and fourteen thousand of the inhabitants perished; and, at the same time, not above two or three of the Europeans who were settled there escaped. The effects of the violent heats we endured were, an entire loss of appetite, a faintness and gripes, with frequent and bilious stools; which greatly exhausted our strength. My stomach was often so weak, that it could receive only a little milk. Several of us became feverish through the excessive heat, and were obliged to have recourse to gentle vomits, &c. Though we were furnished with the most ample conveniencies for travelling, which money, or the strongest recommendations to the principal christians, as well as mahometan chiefs, could procure, and had laid in a quantity of excellent madeira, claret, and other provisions, &c. yet most of us suffered in our constitutions by this long and fatiguing journey.”

On these climates in general Dr. Lind observes, that in well cultivated countries, such as China, the air is temperate and wholesome; while the woody and uncultivated parts prove fatal to multitudes accustomed to breathe a purer air. In all places also, near the muddy and impure banks of rivers, or the foul shores of the sea, mortal diseases are produced from the exhalations, especially during the rainy season. “There is a place near Indrapour, in Sumatra, where no European can venture to remain, or sleep one night on shore, during the rainy season, without running the hazard of his life, or at least of a dangerous fit of sickness; and at Podang, a Dutch settlement on Sumatra, the air has been found so bad, that it is commonly called the Plague-Coast. Here a thick, pestilential vapour or fog arises, after the rains, from the marshes, which destroys all the white inhabitants.”

In treating of the diseases of Africa, the same author takes notice of those of Egypt; which country, he says, is rendered unwholesome by the annual inundation of the Nile, and being surrounded on three sides by large and extensive deserts of sand, by which means it is exposed to the effects of that noisome vapour, which, during the summer months, arises from sultry, hot sand. He doth not, however, say, that the true plague originates in this country, either from the inundation of the Nile or any other cause. On the climate of Egypt I shall once more quote M. Savary, who is a strenuous advocate for its healthiness, and is at pains to confute the opinion of Mr. Pauw, and others, who assert the contrary. “Mr. Pauw (says he) pretends, that at present Egypt is become, by the negligence of the Turks and Arabs, the cradle of the pestilence; that another epidemical disease, equally dreadful, appears here, by the caravans of Nubia; that the culture of rice engenders numerous maladies; that the want of rain and thunder occasions the air of the Thebais to acquire a violence that ferments the humours of the human body, &c.” “These assertions (M. Savary observes) have an air of probability, which might impose on people who have not lived in Egypt; but Mr. Pauw has ventured opinions in his closet, without the guidance of experience. In vallies, indeed, enclosed by high mountains, where the atmosphere is not continually renewed by a current of air, the culture of rice is unwholesome, but not so, near Damietta and Rosetta. The plains are nearly on a level with the sea; neither hill nor height impedes the refreshing breath of the north, which drives the clouds and exhalations off the flooded fields southwards, continually purifies the atmosphere, and preserves the health of the people; so that the husbandmen who cultivate the rice are not more subject to diseases than those who do not. The heats of the Thebais certainly surpass those of many countries under the equator. Reaumer’s thermometer, when the burning breath of the south is felt, sometimes rises to thirty-eight degrees above the freezing point,[27] often to thirty-six. Were heat the principle of diseases, the Said (Upper Egypt) would not be habitable; but it only seems to occasion a burning fever, to which the inhabitants are subject; and which they cure by regimen, drinking much water, and bathing in the river: in other respects they are strong and healthy. Old men are numerous, and many ride on horseback at eighty. The food they eat in the hot season contributes much to the preservation of their health; it is chiefly vegetables, pulse and milk. In Lower Egypt, the neighbourhood of the sea, the large lakes, and the abundance of the waters, moderate the sun’s heat, and preserve a delightful temperature. Strabo and Diodorus Siculus, who long lived here, did not think the country unhealthy. There is, indeed, an unwholesome season in Egypt. From February till the end of May, the south winds blow at intervals, and load the atmosphere with a subtile dust, which makes breathing difficult, and drive before them pernicious exhalations. Sometimes the heat becomes insupportable, and the thermometer suddenly rises twelve degrees. The inhabitants call this season Khamsin, fifty; because these winds are most felt between Easter and Whitsuntide; during which season they eat rice, vegetables, fresh fish and fruit; bathing frequently, and using plenty of perfumes and lemon juice; with which regimen they prevent the dangerous effects of the Khamsin. But it must not be supposed that this wind, which corrupts meat in a few hours, blows fifty days. Egypt would become a desert. It seldom blows three days together; and sometimes is only an impetuous whirlwind, which rapidly passes, and injures only the traveller overtaken in the deserts. When at Alexandria a tempest of this kind suddenly arose, driving before it torrents of burning sand, the serenity of the sky disappeared, a thick veil obscured the heavens, and the sun became blood-coloured. The dust penetrated even the chambers, and burnt the face and eyes. In four hours the tempest ceased, and the clearness of the day appeared. Some wretches in the deserts were suffocated, and several I saw brought to appearance dead; some of whom, by bathing in cold water, were restored to life.”

The internal parts of the continent of Africa are but little known. The northern parts, containing the States of Barbary, are sufficiently healthy; the middle parts of the western coast, known by the names of Negro-land, Guinea, &c. are extremely unhealthy and pernicious to strangers. Dr. Lind informs us, that, at a distance, this country appears in most places flat, covered with low, suspended clouds; and on a nearer approach heavy dews fall in the night time; the land being every morning and evening wrapped up in a fog. The ground is clothed with a pleasant and perpetual verdure, but altogether uncultivated, excepting a few spots, which are generally surrounded with forests or thickets of trees, impenetrable to refreshing breezes, and fit only for the resort of wild beasts. The banks of the rivers and rivulets are overgrown with bushes and weeds, continually covered with slime, which sends forth an intolerable stench. All places however are not equally unhealthy; nor is any place equally unwholesome at all times of the year. It is only with the rainy season that the sickness commences. But as it would be tedious, and not answer our present purpose, to enumerate those places which are healthy, and those which are not, I shall only extract from Dr. Lind’s work an account of one which seems to be as bad as can well be imagined. It is called Catchou, a town belonging to the Portuguese, and situated in 12 degrees N. lat. “I believe (says the author of this account) there is scarce to be found on the whole face of the earth a more unhealthy country than this during the rainy season. We were thirty miles distant from the sea, in a country altogether uncultivated, overflowed with water, surrounded with thick, impenetrable woods, and overrun with slime. The air was vitiated, noisome and thick, insomuch that the lighted torches or candles burnt dim, and seemed ready to be extinguished; even the human voice lost its natural tone. The smell of the ground, and of the houses, was raw and offensive; but the vapour arising from the putrid water in the ditches was much worse. All this, however, seemed tolerable, in respect of the infinite numbers of insects swarming every where, both on the ground and in the air; which, as they seemed to be produced and cherished by the putrefaction of the atmosphere, so they contributed greatly to increase its impurity. The wild bees from the woods, together with millions of ants, overran and destroyed the furniture; while swarms of cock-roaches often darkened the air, and extinguished even the candles in their flight; but the greatest plague was the musquetoes and sand-flies, whose incessant buzz and painful stings were more insupportable than any symptom of the fever. Besides all these, an incredible number of frogs, on the banks of the river, made such a constant and disagreeable croaking, that nothing but being accustomed to such an hideous noise, could permit the enjoyment of natural sleep. In the beginning of October, as the rains abated, the weather became very hot, the woods were covered with abundance of dead frogs, and other vermin, left by the recess of the river; all the mangroves and shrubs were likewise overspread with stinking slime.”

No doubt these accounts are calculated to inspire us with dreadful ideas of the countries mentioned in them. What could be done by the putrefaction of dead animals and vegetables, certainly would be done here; the produce, however, was not the true plague; not even in Catchou; but “a sickness which could not well be characterised by any denomination commonly applied to fevers; it however approached neared to what is called a nervous fever, as the pulse was always low, and the brain and nerves principally affected,” &c. Certainly if in any country heat, moisture and putrefaction could produce a plague, it would be in this. Yet, in all the places we have mentioned, whether India, Arabia, Egypt, or Guinea, (and we might go through the whole world in the same manner) we have not been able to find either moist heat or dry heat, even when aided by putrefaction, insects, and nastiness of all kinds (not justly chargeable upon any climate;) I say, we have not found the united powers of all these able to produce a plague. Nay, it is even doubtful whether climates can produce those inferior diseases above mentioned. Even Dr. Lind, who appears to be so willing to ascribe every thing to climate, seems embarrassed in this respect. “There are many difficulties (says he) which occur in assigning a satisfactory reason, why in some countries, as in those between the tropics, heavy and continual rains should produce sickness; while in other places, especially in the southern parts of Europe, a want of rain for two or three months in summer brings on diseases almost similar. Upon this occasion (adds the Doctor) I cannot help observing, that there is hardly a physical cause which can be assigned for the produce of any disease, that will not admit of some exceptions: thus, not only the woods and morasses in Guinea are tolerably healthy, with some exceptions, in the dry season; but a few instances might be produced of towns surrounded with marshes and a foggy air, where the inhabitants suffer no inconvenience from their situation, even during the rainy season. Do the impetuous torrents of water poured from the clouds during the rainy seasons, in tropical countries, contain what is unfriendly to health? Thus much is certain, that the natives of such countries, especially the mulattoes, avoid being exposed to these rains as much as possible, and when wet with them immediately plunge themselves into salt water, if near it. They generally bathe once a day, but never in the fresh water rivers, when overflown with rains, preferring at such times the water of springs. Is the sickness of these seasons to be ascribed to the intense heat of the then almost vertical sun; which frequently, for an hour or two at noon, dispels the clouds, and with its direct beams instantly changes the refreshing coolness of the air into a heat almost insupportable?

“Further: As the season of those sudden and terrible storms, called the hurricanes, in the East and West Indies, and tornadoes on the coast of Guinea, partly coincides with that of the rains, do these dreadful tempests in any measure contribute to produce the prevailing sickness at those times? It was remarkable one year at Senegal, that, in the beginning of the rainy season, in the night succeeding one of these tornadoes, a great number of the soldiers, and two thirds of the English women, were taken ill, this garrison before having been uncommonly healthy.

“Lastly: Is it not more probable, as in those countries the earth for six or eight months in the year receives no moisture from the heavens but what falls in dews, which every night renew the vegetation, and reinstate the delightful verdure of the grass, that the surface of the ground in many places becomes hard and incrustated with a dry scurf, which pens up the vapours below, until, by the continuance of the rains for some time, this crust is softened, and the vapours set free? That these dews do not penetrate deep into the surface of the earth, is evident from the constant dryness and hardness of such spots of ground, in those countries, as are not covered with grass and other vegetables. Thus the large rivers, in the dry season, being confined within narrow bounds, leave a great part of their channel uncovered, which, having its moisture totally exhaled, becomes a hard, dry crust; but, no sooner the rains fall, than, by degrees, this long parched up crust of earth and clay gradually softens, and the ground, which before had not the least smell, begins to emit a stench, which in four or five weeks becomes exceeding noisome; at which time the season of sickness commences.”

From these quotations it must certainly appear, that the author himself is dissatisfied with his theory; and that, though in the outset he thought heat and moisture, assisted by the exhalations from putrid animal and vegetable substances, sufficient to produce the disorders of which he treats, yet, on a more minute investigation, he is obliged to acknowledge, that something inexplicable still remains. This he now wishes to solve by unknown properties in the water, by confined exhalations, &c. But as the consideration of these things belongs properly to the next section, I shall here only remark, that there hath not yet been given any satisfactory account of the origin of epidemic diseases of what I call the inferior kind, much less of the true plague, which stands above them all, as I have already said, like the serpent Python above other serpents.

To what has been quoted from Dr. Lind, I shall here subjoin the testimony of Dr. Clark, who had an opportunity of observing the epidemic diseases which raged at Bengal in 1768 and 1769. These were, “the remittent fever and dysentery, which begin in August, and continue till November. During the beginning of the epidemic, the fever is attended with extreme malignity and danger; frequently carrying off the patient in twelve hours; and, if not stopped, generally proves fatal on the third or fourth day. In August the remissions are very imperceptible; in October they become more distinct; and, as the cold weather comes on, the fever becomes a regular intermittent. At that time, too, the putrid dysentery begins to rage with the fever. These diseases were very fatal to many Europeans, particularly new comers, in 1768. But in the year 1770, when there was a scarcity of rice, it was computed, that about eighty thousand natives, and one thousand five hundred Europeans, died at Bengal. The streets were covered with funerals; the river floated with dead carcases; and every place exhibited the most melancholy scenes of disease and death. During the sickly seasons at Bengal, the uncertainty of life is so great, that it frequently happens that one may leave a friend at night in perfect health, who shall not survive next day. There have been several instances of persons who have returned home in a state of perfect health from performing the last duties to a deceased friend, and have next day been numbered with the dead. But the cool, agreeable season, from December to March, is productive of no prevailing diseases. The complaints to be met with are in general the consequences, or remains, of the diseases of the former period. The complaints which the Europeans are subject to in the dry months are, the cholera and diarrhœa. Fluxes and fevers are then seldom epidemic; and, when they do happen, are not attended with much danger.

“At Batavia the rainy season is from November to May, during which time malignant, remitting and continued fevers and the dysentery rage with great fatality. Captain Cook, in his first voyage, arrived here in October 1779; the whole crew, excepting Tupia, a native of Otaheite, being in the most perfect health. But, in the course of nine days, they experienced the fatal effects of the climate, and buried seven people at Batavia. On the 3d of December, the ship left the harbour. At that time the number of sick amounted to forty; and the rest of the ship’s company were in a very feeble condition. When the ship anchored at Prince’s Island, in the Straits of Sunda, the sickness increased, and they buried twenty-three persons more in the course of about six weeks. The Grenville Indiaman, which touched at this island in 1771, suffered equally from the malignity of the air. A few were taken on board, when the ship sailed from Batavia, ill of a malignant fever; which spread by contagion at sea, and carried off great numbers. I visited several in this ship, when she arrived at China, who were reduced to mere skeletons, by the duration of the fever and dysentery; both of which were most certainly propagated by contagion.

“Those parts of Sumatra lying immediately under the line are continually subject to rain, and the ground near the shore is low, and covered with thick trees and underwood. The heat being intense, noisome fogs arise, which corrupt the air, and render the country fatal to foreigners. The land of North Island, which lies on this coast, near the beginning of the Straits of Sunda, appears at a distance finely variegated; but at the place where the wood and water are to be got it is low, and covered with impenetrable mangroves, and infested with a variety of insects. It is here that most of the East India ships take in wood for their homeward voyage. A Danish ship, in 1768, anchored in this island, and sent twelve of her hands on shore to fill water; where they only remained two nights. Every one of them was seized with a fever, whereof none recovered: but although the ship went out to sea, none, except the twelve who went on shore, were attacked with the complaint.”

With regard to China, this author says, that the “port of Canton is by no means so healthy as is generally represented. The comparative degree of health which Europeans enjoy here has been ascertained from the instances of the supercargoes, which is, however, a very erroneous standard. The generous and regular way in which these gentlemen live, for the most part, exempts them from diseases; and, being but few in number, no great mortality can take place among them. But seamen, who never observe much regularity in their way of living, who work hard in the day time, are but badly clothed, and not provided against the damps and cold north-easterly winds at night, seldom fail to be afflicted with the diseases already mentioned (fevers and fluxes.) Even the factors of different nations, who reside here for any considerable time, experience all the inconveniences peculiar to any sultry climate: florid health is a stranger to their countenances; their constitutions are soon weakened and enfeebled; and they become subject to habitual fluxes and other complaints, the usual consequences of too great relaxation.”

The climate of the southern part of China, according to the same author, is excessively hot during the summer months. Even in September and October, when the nights are cold, the days continue to be sultry. The cold months are, December, January and February; “and during this time the vicissitudes of the weather are more quick than in any other part of the world. When the wind is northerly, and the thermometer at 46, upon a change of the wind to the south, it is next day up to 60 or 70. People who reside here are always at a loss with regard to their clothing; one day finding a silk coat sufficient; and the next, upon a sudden change of wind, finding it necessary to wear a flannel waistcoat.”

On the subject of climate, therefore, I must conclude with the following observations:—First: That, as the diseases above mentioned are produced both in moist and dry countries, in those in the torrid and those in the temperate zone, they can neither be the offspring of moisture or drought, of heat or cold, of septics or antiseptics, but of something not yet discovered. Second: That, upon fair investigation, it does not appear, that ancient historians have been able to ascertain the origin of any plague whatever: they have universally ascribed it to the anger of the Deity, while their own pride would never allow it to have originated in any country with which they were connected. Third: It doth not by any means appear, that the climates of those countries, where the plague is known to be most common, are at all inferior to those already described, excepting the very circumstance of having the plague frequently in them: nay, indeed, that they are equally bad. Nobody will pretend to argue, that the climate of Asia Minor, of Greece, of the Morea, or of any of the countries most infected with the plague, was, or is, worse than that of Catchou in Africa, already described; yet it is certain, that we have a number of testimonies that the plague has ravaged Asia Minor, while we have not one of its visiting Catchou. Ancient Greece, the Peloponnesus (Morea) and Asia Minor, were accounted healthy and fine countries; and modern travellers assure us, that they have not degenerated in this respect; yet these countries are desolated by the plague, while the unwholesome regions above described are entirely free from it, unless imported from some other quarter. To give this matter, however, as fair a discussion as possible, I shall here consider the account we have of the climate of Bassorah, given by the gentleman residing there in 1780; whose case, in the remitting fever, is given, Appendix, No. VI. “The overflowing of the Euphrates, and its waters stagnating in the desert, have always been accounted primary causes of epidemical diseases at Bassorah. The great floods from the melting of the snow on the mountains of Diarbekir, the ancient Assyria, happened in the year 1780, early in the month of May, when the heats in Persia and Arabia begin to be excessive. The desert, which reaches to the gates of Bassorah, is, for many miles, incrusted with a surface of salt; which, when mixed with the stagnated waters, and exposed to the sun, produces the most noxious effluvia. As early as the 25th of May, the town was surrounded by a salt marsh, the heated steam arising from which was, at times, almost intolerable; but the canal that runs through a great part of the city being filled with the bodies of animals, and all kinds of putrid matter; and, at low tides, all these substances exposed to the sun, made the air in the town scarce supportable; and, being totally destitute of police, the streets were in many places covered with human ordure, the bodies of dead dogs and cats, &c. which emitted a stench more disagreeable and putrid than any thing I ever experienced in my life. As to the degree of solar heat, it far exceeded what I conceived the human frame to be capable of bearing. The sensation under this heat was totally different from what I had ever experienced; it resembled the approach of an heated substance to the body. The quicksilver, in Fahrenheit’s thermometer, rose to between 156 and 162 degrees.[28] From the 30th of May I never saw it so low as 156, but generally between 158 and 160. After I left Bassorah I was told that it rose still higher. In the coolest part of the house, with the aid of every invention to decrease the heat, the quicksilver rose to 115; but after I came away, I was informed that it rose still higher, even at seven in the morning, the hour which we accounted the coolest in the day. Once the heat was said to be so intolerable, that no one could expose himself to it long enough to observe the thermometer in the sun. Some of the oldest inhabitants of Bassorah said that they never remembered to have heard of such a heat in any part of Persia or Arabia. The natives of the country appeared more alarmed at the heat than the Europeans: nothing could induce them to expose themselves to the sun after ten o’clock. I left Bassorah for Aleppo on the 30th of May. On our arrival at Zabira, the heat was so intense, that even the Arabs sunk under it.”

From this account it was natural to expect that violent sickness would ensue. This was the opinion of the inhabitants, and they were not deceived. The sickness, however, was not the true plague, but a violent remitting fever; and even this did not originate in the city itself, but was observed to approach from Asia Minor, ravaging Diarbekir, and keeping the course of the Tigris, to Bagdad, where many died. From thence it followed the course of the Euphrates to Bassorah, and for about twenty miles lower. The opposite, or Persian shore, though within a few miles, was exempted, and it did not spread more than twenty miles into the desert.[29]

I might now proceed to give an abstract of what has been said of the power of climate in producing diseases on the Western Continent, and West India islands; but as this belongs more especially to the second part of this Treatise, I shall here pass it over, as well as what Dr. Smith has said of the climate of Greece, in the Medical Repository, and which he endeavours to prove to be similar to the climate of North America. But, before we proceed to consider what diseases may be produced by climate alone, it is proper to discuss the question, how far man is naturally subject to diseases of any kind? Many, no doubt, will be apt to suppose this a very absurd question; for as man is now, by nature, subject to death, it seems to follow, that he is also naturally subject to disease, as the means of bringing on death. But, however plausible this may appear, experience shows, that disease and death are not always connected. Many people die of mere old age; the powers of life being exhausted, and the system so far decayed, that the various parts of it can no longer perform their offices. On the other hand, a disease destroys by attacking some particular organ, and either totally consuming or altering it in such a manner, that it disturbs the vital operations, while yet strong and vigorous. We may therefore compare the death of a person from mere old age to the natural extinction of a candle when the tallow is totally consumed; and death from disease, to the blowing out of a candle while a part of it remains, and might have burned for a considerably longer time. Thus I am inclined to consider all diseases as merely accidental; and this with the greater certainty, because, though, in common with other believers in revealed religion, I think that death is the consequence of Adam’s transgression, yet I do not find that disease of any kind was threatened except in cases of positive transgression, long after the days of Adam.

Every one allows, that, though some diseases are natural, some are likewise artificial; but nobody hath attempted to draw the line of demarcation between them. Every thing is charged upon climate, heat, moisture, drought, vapour, &c. and yet, upon examination, we shall find the utmost difficulty in deriving a single disease from the causes we assign. No person in his senses will say that Adam, in consequence of eating the forbidden fruit, became liable to the venereal disease. As little can we say for the gout, the stone, or the dropsy; and if we cannot particularize the diseases to which he became naturally liable, we have no right to say that any kind of disease became natural to him in consequence of his transgression. If, therefore, death itself, originally not natural to man, did yet take place in consequence of his moral conduct; and if diseases, without number, have arisen among his posterity, though not natural to him in consequence of his first transgression, we have equal reason to believe that these diseases have taken place among them in consequence of their moral or rather immoral conduct, in totally deviating from the line prescribed them by their Maker, and following others of their own invention; and this will appear the more probable, when we consider, that, long after mankind became subject to death, we find diseases, particularly the pestilence, threatened as the consequence of subsequent transgressions.

If, without taking scripture into consideration, we attend only to what may be gathered from profane history, we find the testimony of all the ancients concurring in one general point, viz. that in times of great antiquity men were more healthy, and even stronger, than in the times when those authors lived. This is taken notice of by Homer, when comparing the strength of men in the time of the Trojan war with those in his days, about two centuries later.[30] Virgil, who lived in much more modern times than Homer, carries his ideas of the degeneracy of man much farther; and informs us, that Turnus, when fighting with Æneas, took up and threw a stone which twelve men of that time could not have lifted. Now, though we know that both these accounts are fabulous, yet they perfectly coincide with the voice of historians of all nations; for we are universally told, that the first inhabitants of countries were a brave, hardy people, living according to the simplicity of nature, free from diseases, and attaining to a good old age.

This is so conformable to what is generally said at present, probably very often by rote, without regard to rational evidence, that, were we so inclined, ample room might be found for declamation against modern luxuries, particularly the practice of drinking ardent spirits, as pernicious to health, and destructive to the human body. On this subject, however, we may once for all observe, that, although we find ample evidence of the baleful influence of these liquors in producing other diseases, yet we find none of their ever having had any share in the production of an epidemic or general disease among mankind. In ancient times the art of distillation seems to have been unknown; so that whatever mischief was done in those days must have been done by wine, or other fermented liquors. In modern times, though the use both of fermented liquors and ardent spirits is undoubtedly carried to excess, yet there is no evidence of their producing an epidemic, or even making it more violent or general than it would otherwise have been. Dr. Cleghorn, having spoken largely of the manner of living of the natives in Minorca, proceeds thus: “I should next give a circumstantial account of the diet and way of life of the British soldiers in this island; but as this would be a disagreeable task, I shall only observe, that the excess of drinking is among them an universal vice, confirmed into habit. But, however different the Spaniards be from the English, in their meat, drink, exercise, affections of the mind, and habit of body; yet the health of both nations is equally influenced by the seasons. An epidemical distemper seldom or never attacks the one class of inhabitants without attacking the other also; and, surprising as it may appear, it is nevertheless true, that the peasants, remarkable for temperance and regularity, and the soldiers, who, without meat and clothes, frequently lie abroad drunk, exposed to all weathers, have diseases almost similar, both as to their violence and duration.”

There can be no doubt that excess in drinking hath put an end to the lives of many individuals; and it hath been observed, that such as attempt to preserve themselves from the plague by the use of strong liquors, have generally fallen sacrifices to it;[31] but this cannot prove that such excess would have brought on the distemper without some other cause. It hath been certainly found, that excess in drinking or eating, excess in venery, excessive fatigue by labour, watching, study, &c. will all make an epidemic disease more violent when it attacks a particular person; but no experience hath yet shown that the first person seized with an epidemic always fell under this description. All that can be said on the subject is, that, by such excesses as have already been described, the body is prepared for receiving the disease, by an exhaustion, or evaporation (if we please to call it so) of the vital principle; as wood is prepared for burning by the evaporation of its moisture; but as wood, however dry, will not burn without the contact or application of fire, so neither will the body, though ever so well prepared, be attacked by any epidemic, unless the true cause of that epidemic be also applied.

Thus we are still disappointed in our attempts to discover the origin of the plague. We have seen that the most unhealthy climates in the world do not produce it of themselves; neither can the conduct of any individual bring it upon himself, without an unknown something, which nobody has yet found out. It was this difficulty of finding out the natural cause, which certainly induced by far the greatest number of writers on the subject to ascribe it to Divine Power; and even as late a writer as Dr. Hodges tells us, that he believes in the to Theion, the “finger of God,” in the plague, as much as any body. As for those who have endeavoured to account for the origin of this distemper from an inquiry into natural causes, and conclusions drawn from the late experiments on air, they have totally failed; as will be fully elucidated in the following section.

If then we are to believe that diseases, especially those called epidemics, among which the plague holds the first place, have arisen in consequence of a certain line of conduct adopted by the human race, or have been inflicted by the Deity as punishments on that account, we are to look for their origin among those to whom the Deity principally manifested himself; that is, the Jews, and nations who interfered with them. Among the Jews we hear of the first general plague distinctly mentioned; viz. the three days pestilence of David, and to which it is possible that Homer alludes in his Iliad. Next to this is the great plague of 767 B. C. said to have spread all over the world. This coincides with the time of Pul, king of Assyria; who, having overthrown the ancient kingdom of Syria, turned his arms against that of Israel, and no doubt extended his conquests among the eastern nations, as we know very well the Assyrian monarchs did. As the ten tribes, ever after their separation from the house of David, had in a manner totally given themselves up to idolatry, we are not to wonder if the pestilence, so frequently threatened by Moses, was very common, or, as physicians term it, endemic, among them. Thus, whatever enemy invaded the country, would almost certainly carry the disease along with them, and spread it among the other nations with whom they afterwards had any connexion. At this time, or even before this, during the wars of Syria with Israel and Judah, this dreadful pestilence might begin; but, as to its being all over the world in any particular year, I do not see how it can be ascertained; because there are no general histories of the world in those early times. It appears more probable that this general pestilence took place at the time that Sennacherib’s army was destroyed. I have no doubt, indeed, for the reasons already given, that the plague had infected Sennacherib’s army before he went into Ethiopia. In that country, in all probability, he would leave it; and, after his return to Judea, when the dreadful catastrophe befel him of an hundred and eighty-five thousand of his men being destroyed in one night, there can be no doubt that the remains of his army would carry with them the seeds of a most malignant pestilence, capable of spreading destruction far and wide. It is true, we are not directly told, in Scripture, that the Assyrian army was destroyed by a plague, but that the angel of the Lord destroyed them; but, as this expression is quite similar to what we read of the pestilence in David’s time, there can be but little doubt that the means of destruction made use of in both cases were the same. Josephus expressly says, that Sennacherib’s army was destroyed by a pestilence. Neither are we to conclude, because this pestilence was miraculous, that it therefore certainly killed every one on whom it fell; or that it would not infect those who came near the sick, as any other disease of the kind would do.

From the same source may we derive the propensity in the Carthaginian armies to pestilential disorders. Carthage was a colony of Tyre; and the Tyrians were in close alliance with the Jews, during the reigns of David and Solomon, and very probably afterwards; so that from them the distemper might be communicated in such a manner as to be almost endemic; and thus hardly an army could be sent out but what would have the infection with it, breaking out with violence now and then, as occasional causes tended to give life to the contagion. It is impossible, however, from the source just mentioned to trace the plague of Athens, or the first plague in Rome; but it is very natural to suppose that the violent one which raged in Rome, during the reign of Titus, came from Jerusalem. That city had sustained a most dreadful siege, and the obstinate and wretched inhabitants had endured such calamities as have scarcely been recorded in the history of nations. Among these calamities was a pestilence, which, in all probability, would be conveyed to Rome, and there occasion the destruction already mentioned.

But what seems to render this account of the origin of the plague more probable is, that the Jews are to this day accused of propagating the disease in those countries where it is most frequent. Baron de Tott is of opinion that the plague in Constantinople originates among the Jewish dealers in old clothes; for these avaricious dealers, purchasing the infected goods, sell them indiscriminately to every one who will buy, and that without the least care taken to remove the infection from them; by which means it is no wonder to find the plague, as well as other diseases, disseminated among them in great plenty. Dr. Russel informs us, that the Jews are most liable to the plague, the most fearful of it, and the most ready to fly from the infection. The Abbe Mariti agrees in the same accusation against this unfortunate people. “The Jews (says he) purchase at a low price the goods and wares which remain when most of the family are deceased, and then store them up; which, when the plague is over, they sell at a dear rate to those will buy, and thus propagate the pestilential poison: again it kindles, and presently causes new destruction. Thus this opprobrious nation, preferring gold to life, sell the plague to mussulmen, who purchase it without fear, and sleep with it, till, renewed of itself, it hurries them to the grave.” M. Volney, though he does not mention the Jews in such express terms as Mariti and Russel, yet agrees as to the mode of its propagation in Constantinople, and the reason of its continuance in that city. “It is certain (says he) that the plague originates in Constantinople, where it is perpetuated by the absurd negligence of the Turks, which is so great, that they publicly sell the effects of persons dead of the distemper. The ships which go to Alexandria never fail to carry furs and woolen clothes, purchased on these occasions, which they expose to sale in the bazar of the city, and thereby spread the contagion. The Greeks who deal in these goods are almost always the first victims.”

Thus the account we have of the origin of the plague at present is, that the city of Constantinople, having been long and deeply infected, the infection is stored up through the avarice of the Jewish merchants, who buy the goods and clothes of the infected. The stupidity of the Turks allows these goods to be sold in Constantinople, or exported freely to all parts to which their vessels sail, particularly to Alexandria; where the avarice of the Greeks prompts them to buy without examination or precaution, to the destruction of their own lives, and of multitudes of others. Egypt being the principal place of traffick, the plague is more frequent there than in other parts of the empire. Syria is comparatively free from it; which M. Volney supposes to be owing to the small number of vessels which come there directly from Constantinople.

In this way we may, in a pretty plausible manner, account for the origin of this distemper; viz. that it originally fell upon the Jews as a punishment for their iniquities; that from the Jews it has been at different times conveyed to other nations; and, by a mixture of those nations, has, at times, become general all over the world. At last it has, by the avarice of that people who first had been the occasion of its being introduced into the world, become permanent in Constantinople, whence it is still diffused among different nations in proportion to their dealings with that capital.

But it may now be said, ‘Allowing the positions contended for to be true in their utmost extent, how comes it to pass that the plague hath not been general in every age and in every country? Since the destruction of Jerusalem, the Jews have been dispersed over all nations: if nothing then were wanting to produce a pestilence but Jews and old clothes, no age or country ought to have been free from it; nevertheless it is certain that violent plagues take place only at particular times, with long intervals between; and of late the pestilential disposition seems to have become much less frequent than formerly; the western parts of Europe, particularly Britain, having been free from it for a great number of years. There must therefore be some cause, different from what has yet been mentioned, by which the infection is occasionally roused from inactivity, and excited to spread desolation all around.’

That there are predisposing causes to epidemic disorders, especially to the plague, the most fatal of them all, is not denied. These prepare the body for receiving the infection, but they will not, without that infection, produce the disorder. Of these causes so many are to be found in the conduct of mankind themselves, that we scarcely need to look for them any where else. In looking over the histories of plagues, we find them in an especial manner connected with famines and wars. The former sometimes take place in consequence of the failure of crops through natural causes; but, considering the general fertility of the earth, we must certainly account it owing to bad management, in some respect or other, that every country hath not as much laid up within itself as would guard against the consequences of at least one or two bad crops. Yet we believe there is not, at present, a country upon earth in this predicament. If a crop fails any where, the inhabitants must import largely, or they must starve. This is the case even in the fertile regions of the East, where the earth produces in excessive abundance,[32] and there is little or nothing of any kind of provision exported to other countries. A remarkable instance of this occurred in the plague at Aleppo, a history of which is given by Dr. Russel. He tells us, that the winter of 1756 proved excessively cold, which was followed by a famine next year. This account is confirmed by Mr. Dawes, in a letter to the bishop of Carlisle.[33] He tells us, that in the course of the winter many perished through cold; that the inhabitants were reduced to such extremities, by the single failure of the crop in 1757, that women were known to eat their own children as soon as they expired in their arms with hunger; and that human creatures might be seen contending with dogs, and scratching for the same bone with them in a dunghill. A dreadful plague followed; which, the two succeeding years, swept off not fewer than sixty thousand in the city of Aleppo.

It is probable that in this case the famine either produced the plague, or made it worse than it would have otherwise been; and it is not denied that the cold and bad season was the direct cause of the famine. But as little can it be denied, that had the people, or their governors, been so provident as to have laid up stores sufficient to supply the country for one year, this famine would not have been felt. As far, therefore, as the plague was connected with the famine, we must own that it was chargeable on the human race themselves; not the sins of this or that particular person, but a general deviation from the task assigned them by their Maker, viz. that of cultivating the ground; and, instead of this, spending their time in folly and trifling, to say no worse.

But famines are occasioned not only by natural causes, but by wars; in which mankind, acting in direct opposition to the laws of God and nature, destroy and lay waste the earth, taking every opportunity of reducing to extremity both those whom they call innocent and those whom they call guilty. Thus vast multitudes are reduced to want, to despair, and rendered a prey to grief, terror, and every depressing passion of the human mind; they are exposed to every inclemency of the weather; to the scorching heats of the day, and the chilling damps of the night; in short, to every thing that we can conceive capable of predisposing the body for the reception of diseases of the very worst kind. No wonder therefore that war and pestilence go hand in hand; and, by taking a review of the history of mankind, we shall see, that, always at those times when the nations have been most actively employed in the trade of butchering one another, then, or very soon after, they have been afflicted with pestilence. To begin with the great plague of 767 B. C. which coincides with the rise of the Assyrian empire: Till this time, though there had been numberless wars, yet they were carried on upon a much smaller scale than now, when great empires were to be set up, and when the most distant nations were to be assembled in order to gratify the pride and ambition of an individual. The Assyrians, we know, penetrated into Ethiopia; but how far east or how far west they went, we are not certainly informed. To their wars, however, we may with reason ascribe the desolations occasioned by this first plague. From Thucydides’s account of the plague at Athens, it seems plain that it was occasioned, or at least rendered more violent, by the wars of the Greeks with one another at that time. Had the Carthaginian army staid at home when they went to war with Dionysius, tyrant of Syracuse,[34] it is very probable that the pestilence would not have broke out among them. The like may be said of the plague which broke out among them in the time of Marcellus.[35] That in the time of Jugurtha, indeed, is said to have been occasioned by locusts; but, had not vast bodies of men been collected together for the purposes of war, the plague could never have committed such ravages. The plague in the time of Titus could not have been brought from Jerusalem, nor perhaps would it have existed there, had not Titus made war against that city; and so of others.

The plague which began in the reign of Justinian, as it was more violent than any recorded in history, so it was preceded by wars equally unexampled. The Romans had indeed for ages employed themselves in war; but, by their constant superiority to every adversary, their empire had become so amazingly extensive, that, whatever wars were carried on in the remote provinces, the great body of the empire always remained at peace; and this was the case even in their most violent civil wars. On the accession of Alexander Severus, about the year 232, they began to encounter enemies so numerous and formidable, that all their power proved insufficient to repel them. In the tenth year of Alexander’s reign, the Persians, having overthrown the ancient empire of the Parthians, turned their arms against the Romans, and, though frequently defeated at that time with great slaughter, renewed their incursions in the reign of Gordian, about the year 242, when they were in like manner defeated and obliged to retire. As these defeats, however, did not at all affect the strength of the Persian empire, the Romans still found them as formidable enemies as ever; while the Goths, Sarmatians, Franks, and other northern nations, harassed them in other parts. In the reign of Decius, who ascended the throne in 249, they became extremely formidable, insomuch that the emperor himself, with his whole army, was at last cut off by them. The consequence of this was, that the empire was instantly invaded in many different parts, and, though the barbarians were at times defeated, we never find that the empire regained its former tranquillity. The Persians and Scythians, taking advantage of the general confusion, invaded the provinces next them, while the finishing stroke seemed to be given to the Roman affairs by the defeat and captivity of Valerian by the Persians.

This disaster, as may well be imagined, produced an immediate invasion by numberless barbarians, while such multitudes of pretenders to the imperial crown were set up, each asserting his claim by force of arms, that the whole Roman territories were filled with bloodshed and slaughter. At this time Gallienus, the son of Valerian, was the lawful emperor, if indeed we may apply the word to the domination of such a monster. His mode of government may be imagined from the following letter written to one of his officers in consequence of a victory gained over an usurper named Ingenuus. “I shall not be satisfied with your putting to death only such as have borne arms against me, and might have fallen in the field: you must in every city destroy all the males, old and young; spare none who have wished ill to me, none who have spoken ill of me, the son of Valerian, the father and brother of princes. Ingenuus emperor! Tear, kill, cut in pieces, without mercy: you understand me; do then as you know I would do, who have written to you with my own hand.” In consequence of this horrible order, not a single male child was left alive in some of the cities of Mœsia, where this inhuman tragedy was acted.

In the midst of this dreadful commotion, we find the pestilence contributing its share to the common work of desolation. In Alexandria in Egypt, says Dionysius, bishop of that place, “fury and discord raged to such a degree, that it was more easy to pass from the east to the remotest provinces of the west, than from one place of Alexandria to another. The inhabitants had no intercourse but by letters, which were with the utmost difficulty conveyed from one friend to another. The port resembled the shores of the Red Sea strewed with the carcases of the drowned Egyptians: the sea was dyed with blood, and the Nile choked up with dead bodies. The war was attended with a general famine, and the famine with a dreadful plague, which daily swept off great numbers of people, insomuch that there were then in Alexandria fewer inhabitants, from the age of fourteen to that of eighty, than there used to be from forty to seventy.” It was not in Egypt alone that this calamity prevailed. It raged with great violence in Greece, and at Rome itself; where, for some time, it carried off five thousand persons a day. Many terrible phenomena of nature took place at the same time. The sun was overcast with thick clouds, and great darkness took place for several days, attended with a violent earthquake, and loud claps of thunder, not in the air, but in the bowels of the earth, which opened in several places and swallowed up great numbers of people in their habitations. The sea, swelling beyond measure, broke in upon the continent, and drowned whole cities.[36]

At last the civil commotions were settled by the accession of Claudius to the empire in 268. He found the Roman force so exhausted, that, when marching against the Goths, he wrote to the senate in the following terms: “If I should not be attended with success, you will remember that I fight after the reign of Gallienus. The whole empire is quite spent and exhausted, partly by him, and partly by the many tyrants who, during his reign, usurped the sovereignty, and laid waste our provinces. We want even shields, swords and spears.” In this miserable plight, however, he gained a most extraordinary victory; three hundred thousand of the enemy being killed or taken. But, while Claudius thus carried on the work of death successfully against the barbarians, he was attacked from a quarter where he could make no resistance: a violent plague broke out in his army, and carried off himself and a vast number of his men.

The dreadful defeat given to the Goths did not long preserve the tranquillity of the empire. New invasions took place, and new massacres ensued. At last, on the accession of Dioclesian to the empire, it was thought proper, on account of the present emergences, to divide such wide-extended territories into four parts, to be governed by four emperors of equal authority. By the activity and valour of these, particularly of one of them, named Galerius, the northern barbarians were repressed, and the Persians reduced so low, that they were obliged to yield up a great part of their territories; and it is said that their country might even have been reduced to a Roman province, had the emperor so inclined. We know not whether, in his eastern expedition, the Roman army received any infection, nor do we hear of any plague breaking out in it; but we are told that Galerius himself died of an uncommon distemper; an ulcer, attended with mortifications, violent pains, and the production of an infinite number of vermin, which devoured and tormented him day and night. This distemper, however, seems rather to have been a cancer than a pestilential disorder, as he laboured under it for more than a year. After his death, dreadful wars continued, both by reason of the incursions of barbarians, and the contests of those who enjoyed, or wished to enjoy, the empire. The eastern parts, however, had for some time kept free from pestilential contagion; of which the christian writers say, that Maximin, who reigned there, had made his boast; and, being a heathen, ascribed it to the care he took of preserving the worship of the gods. But, if this was really the case, he soon found his gods unable to protect him; for, soon after the accession of Constantine the great, and his embracing christianity, the dominions of Maximin were afflicted with famine accompanied with pestilence, and that attended by symptoms of a most extraordinary nature; particularly ulcers about the eyes, which rendered multitudes of those who were infected with the distemper totally blind. The christians did not fail to ascribe this plague to the sins of Maximin; but it must be observed, that to his other sins he had added that of involving himself in a violent war, during which the pestilence broke out, and which probably was one of the causes of it. We may likewise observe, that if the sins of Maximin brought on the plague, the piety of Constantine could not keep it off; since we find that in the year 332, a considerable time after the death of Maximin, the territories of Constantine were ravaged by a dreadful plague, and the famine was so severe, that, at Antioch, wheat was sold at four hundred pieces of silver per bushel. The distemper which put an end to the life of Maximin himself was indeed so extraordinary, that we may reasonably excuse those who called it a judgment sent directly from heaven. His eyes and tongue are said to have putrefied; “an invisible fire was kindled in his bowels, which, being attended with unrelenting torments, reduced him in a few days to a perfect skeleton; his whole body was covered over with a kind of leprosy, and devoured by swarms of vermin; he could not be prevailed upon to take any nourishment, but greedily swallowed handfuls of earth, as if he had hoped by that means to assuage his pains, and allay the hunger with which he was tormented without intermission.”[37] All this, we are told, was the effect of poison, which he had swallowed in despair, after being defeated in battle; but the symptoms are unaccountable.

After the death of Constantine, the empire being again parted, civil dissensions took place; the northern barbarians and Persians renewed their incursions, and at length the battle of Mursa, between the emperor Constantius and an usurper named Magnentius, destroyed such numbers that the empire no more recovered its former strength. From this time therefore the wars with the barbarians became more and more violent; and, though frequently overcome, the advantage was ultimately on their side. In 361, the first year of the emperor Julian, the pestilence again made its appearance. It was accompanied by many other grievous calamities: Dreadful earthquakes were felt in every province; most of the cities in Palestine, Libya, Sicily and Greece, were overturned. Libanius writes, that not one city in Libya was left standing, and but one in Greece; that Nice was utterly ruined, and Constantinople greatly damaged. The sea, in several places, broke in upon the land, and destroyed whole cities with their inhabitants. At Alexandria, the sea, retiring during an earthquake, returned again with such violence, that it drowned several towns and villages in the neighbourhood. The earthquakes were followed by a famine, and the famine by a pestilence. It was observed by the christian writers, that the famine seemed to follow Julian from place to place: and no wonder that it did so; for he not only had always a large army along with him, which consumed great quantities of provision, but, attempting to remedy the evil by fixing the prices of provisions, he rendered it much worse, as the dealers in corn were thereby tempted to convey it to other places.[38] Indeed this emperor seems to have been inclined to produce famines wherever he went; for, on his entering the territories of the Persians, with whom he was at war, he wasted the country to such a degree, that he could neither subsist nor return; while the enemy, imitating his example, destroyed all before him. The consequence was, that, by the time Julian was killed, the famine raged in the Roman camp to such a degree, that not a single person could have escaped, had not the enemy mercifully granted them peace.

Notwithstanding this dismal situation, we hear of no plague invading the camp of the Romans at that time. The wars, however, continued with great violence; and, in the time of Valentinian, Valens and Gratian, became worse than ever. The dreadful state of the empire in the time of Gratian is thus described by St. Jerom: “The whole country, from Constantinople to the Julian Alps, has been swimming these twenty years in Roman blood. Scythia, Thrace, Macedon, Dardania, Dacia, Thessaly, Achaia, both Epiruses, Dalmatia, both Pannonias, are filled with Goths, Sarmatians, Quadians, Alans, Huns, Vandals, Marcomans, &c. whose avarice nothing has escaped, whose cruelty has been felt by persons of all ranks, ages and conditions.” “What evils, (says Gregory Nazianzen) have we not seen or heard of! Whole countries have been destroyed with fire and sword; many thousand persons of all ranks and ages have been inhumanly massacred; the rivers are still dyed with blood, and the ground covered with heaps of dead bodies.”

In the midst of so great calamities, the pestilence, as an evil of inferior nature, might in many cases pass unnoticed by the historians of the times; nevertheless, even during that distracted period, we find some accounts of it. In 384 we are told of a famine and plague at Antioch; and, in 407, of one in Palestine, said to be occasioned by multitudes of grasshoppers, which even obscured the sun, and turned day into night. After having done incredible mischief, they were thrown by the wind partly into the Red Sea, and partly into the Mediterranean; whence being again cast ashore by the waves, they putrefied, and occasioned a pestilence. Two years after, when Rome had been first besieged by Alaric the Goth, the city was reduced to such straits, that human flesh was publicly sold, and some mothers are said to have devoured their children. This terrible famine was occasioned by the uncultivated state of the country, which had lain waste for several years, by reason of the wars, and the ports of Africa being blocked up by Heraclianus lest an usurper should become emperor; and thus this loyal admiral, for fear that the people should have a bad governor, determined rather that there should be no people to be governed. Notwithstanding this terrible famine, however, we hear of no pestilential disorder taking place; not even after the taking of the city by Alaric, when bloodshed and massacre were added to the other calamities.

All this time the empire, by the incursions of barbarians, by usurpations, civil wars, and the general licentiousness of the people, had been in a situation not to be described. The invasion of the Hunns, a new and more formidable enemy than they had ever experienced, now completed the ruin of the Romans. The whole western part of the empire became one continued scene of carnage and desolation. The common epithet bestowed upon Attila, the king of these barbarians, was, “The Scourge of God, the Destroyer of Armies.” As a specimen of his behaviour, we shall select the account of his taking of Aquileia in 452. That city, “being well fortified, and defended by the flower of the Roman troops, held out, in spite of his utmost efforts, for three months; at the end of which it was taken by assault, pillaged for several days together, and laid in ashes; not a single house being left standing, nor one person alive that fell into the enemy’s hands. The cities of Trevigio, Verona, Mantua, Cremona, Brescia and Bergamo, underwent the same fate; the barbarians raging every where with such fury as can hardly be expressed or conceived, and putting all to the sword, without distinction of sex, age, or condition.”[39]

Every one must own that this was a very effectual method of preventing the plague in those cities. It did not, however, prevent that, or some other diseases, from destroying such numbers of the tyrant’s troops, that he was for that time prevented from taking Rome itself. From this time, to the total extinction of the western empire, we do not hear of any remarkable infection taking place. The barbarians still continued their wars with one another, while the emperors of Constantinople were likewise at continual variance with the Persians. At last, in the year 532, they concluded what they called a perpetual or eternal peace, which lasted eight years! Other treaties and truces were concluded; notwithstanding which, the war was almost continual in the east; while, by the second conquest of Italy, and the invasion of the Gothic territories, new desolations overspread the west. Thus, for a great number of ages, mankind had been preparing themselves for the dreadful pestilence which was about to ensue. Whatever infection could be communicated to the air by multitudes of carcases rotting above ground had been done in an ample manner. Whatever debility could be communicated to the human frame by famine, exposure to the inclemency of weather, by fatigue, terror, grief, and every thing that can render life miserable, had also been communicated by the most powerful means. There only wanted something to begin the calamity; and this, whatever it was, took place in the fifteenth year of Justinian. Mr. Gibbon ascribes the origin of it to locusts; and its universality, to the general mixture of all nations, and the unrestrained intercourse they had with one another. “No restraints (says he) were imposed on the frequent intercourse of the Roman provinces. From Persia to France the nations were mingled by wars and emigrations; and the pestilential odour, which lurks for years in a bale of cotton, was imported, by the abuse of trade, into the most distant regions. Procopius relates, that it spread always from the sea-coast to the inland countries: the most sequestered islands and mountains were successively visited; the places which had escaped the fury of its first passage, were alone exposed to the contagion of the ensuing year. In time, its malignity was abated and dispersed; the disease alternately languished and revived; but it was not till the end of a calamitous period of fifty-two years, that mankind recovered their health, or the air resumed its pure and salubrious qualities.”

Thus Mr. Gibbon endeavours to explain the causes of this plague from an alteration in the salubrity of the atmosphere, without taking into consideration the dreadful commotions among mankind, above related. But, now that we have noticed two very general infections, one in 767 B. C. the other 1300 years after, we find them both preceded and accompanied by wars uncommonly violent and destructive. The great plague in the time of Justinian is said by Mr. Gibbon to have continued only fifty-two years; but this we must understand of its first and most violent attack; for it appears, from the testimonies produced in the former section, that pestilential disorders, even very violent ones, continued at intervals for several centuries. Thus, from the year 541 to 593, the space of fifty-two years is included; nevertheless, in the time of Phocas, who began to reign ten years after, the same calamity continued; as did also violent wars with the Persians and other barbarians.

The year 622 is remarkable for the flight of Mahomet from Mecca to Medina, from which time we may date the rise of the empire of the Saracens; a people who, for desolation and destruction, were perhaps never equalled except by the Hunns and Moguls. In 630 the impostor himself died, after having just united the Arabs or Saracens, and fitted them for the work in which they were to be employed. Their first exploit was, to fall upon the empire of Persia, now weakened by its endless wars with the Romans. This was conquered in two years; after which they broke into Palestine, and conquered the provinces bordering upon Syria. In 634 they reduced Syria itself and Egypt. In 636 they took and plundered Jerusalem. In 642 they conquered the African provinces, and reduced some of the islands in the Levant. With unabated fury they proceeded to the east and west; laying siege, in 668, to Constantinople itself, where they received their first check by the shipwreck of their fleet, and the defeat of their army. Thus, in the space of 38 years, the immense tract of country from the eastern part of Persia to the confines of the Mediterranean Sea, with the northern coasts of Africa, the whole including a space scarce inferior to the empire of Alexander the Great, was reduced under subjection to a race of savage barbarians, who knew only how to plunder, destroy, and reduce other nations to slavery.

In this manner were the eastern parts of the world prepared for a new infection, supposing the old one to have been entirely gone off. The Saracens pursued their good fortune, ravaged and conquered from India to Spain, and from Spain were proceeding northward through France, to extend their conquests to the other countries of Europe. But here, in 728, their fury was stopped by Charles Martel, the father of Pepin, and grandfather of Charles the Great. After a most obstinate and bloody battle, which lasted seven days, and in which the barbarians lost three hundred and seventy-five thousand men,[40] they were driven beyond the Pyrennean mountains, and never after durst enter France. Thus was one fury stopped, only to give place to another. Charles, as ambitious and as cruel as the Saracens, having in vain attempted the conquest of Spain, reduced Italy and Germany; and, having dreadfully massacred the Saxons, and almost exterminated the Hunns, set up the German Empire, and was crowned emperor of the West in 800.

While the nations were thus deluging the earth with blood, the pestilence made its appearance in the east, attended with extraordinary phenomena.[41] Some of these are taken notice of by the Arabian historians, and others are mentioned by them, concerning which the Greek histories are silent. In 636, particularly, we hear of violent storms of hail throughout the Arabian Peninsula, and of Syria being ravaged by epidemic distempers. It would seem, indeed, that the plague, during the whole of these horrible periods, had never been extinguished; for in 671 they tell us that a celebrated Arab, named Ziyad, died of the plague; though neither Greek nor Arabian historians take notice of any remarkable pestilence as raging at that time. We are told that this man was attended by no fewer than an hundred and fifty physicians.[42] “But, as the decree was sealed, and the thing determined, they found it impossible to save him.” This distemper was attended with such an excruciating pain in his right hand, that the unhappy patient had recourse to a cadi, or judge, to inform him whether he might lawfully cut it off. The judge determined that it was absolutely unlawful to do so; notwithstanding which, Ziyad resolved to proceed: but his heart failed him when he saw the instruments and cauterising irons to be employed in the operation; for in those times of barbarity and ignorance they knew no other method of stopping blood but by a hot iron; and therefore some of the physicians in ancient times, when a limb was to be cut off, ordered the incision to be made down to the bone with a red hot razor. But, to return to our subject: In Syria and Mesopotamia swarms of locusts infected the earth about the year 679; but, as it seems extremely probable that the plague was never out of the eastern regions, we cannot expect to hear much of it, unless when extremely violent. That in the time of Constantine Copronymus seems to have extended over Arabia, as we are told that the Khalif Yezid, who was cotemporary with Copronymus, died of the plague. We are also told, that the earthquakes which afflicted the territories of the Greek emperors extended themselves to the countries about the Caspian Sea. In those ages indeed the phenomena of nature appear to have been so extraordinary, that we can scarcely account them any other than miraculous. Some of these have been described in the former section, on the authority of the Greek historians: the Arabians make mention of others similar. They tell us, also, that once or twice it rained black stones, and that some of these were so inflammable, that an Arab having attempted to make a fire with one of them in his tent, it burst out into such a violent flame as consumed the tent altogether.[43] This rain may be accounted for from the explosion of a volcano; but how shall we account for the sun himself losing his light? a phenomenon acknowledged even by Mr. Gibbon; though that author huddles things together in such a manner as seems totally inconsistent with the regular chain of events. He tells us, that the dreadful plague, which broke out in the time of Justinian, was preceded by comets, and most violent earthquakes; and that these comets were attended with an extraordinary paleness of the sun. This may be; but the word paleness cannot apply to the darkness which lasted from the fourth of August to the first of October, and to which he seems to allude, though it happened long after the time of Justinian; neither can it be applied to what I am now about to relate, viz. that in the year 782, a little after sunrise, the solar light was lost without an eclipse, and the darkness continued till noon. It is impossible to read the histories of those times without remembering the words of our Saviour, that there should be signs in the sun and in the moon, distress and perplexity of nations, the sea and waves roaring, men’s hearts failing them for fear, &c. But, however the God of nature might thus intimate to mankind his displeasure with their proceedings, it is certain they made no alteration in their conduct. The Saracens, having conquered immense tracts of country, engaged in civil wars among themselves; the western nations, after having tried in vain to destroy each other, at last united in a romantic design of conquering Palestine from the Infidels; while the Turks, leaving their habitations about Mount Caucasus, where, like the vultures of Prometheus, they had for ages remained unseen and unknown, precipitated themselves upon the Greeks and Saracens, and lastly, as if all hell had broke loose at once, the Moguls, from the most easterly part of Asia, poured destruction upon the countries to the west, even as far as Russia and Poland.

All these events took place in a few centuries. In 844 the Turks quitted Mount Caucasus, and settled in Armenia Major. In 1030 they fell upon the Saracen empire, now divided among innumerable chieftains continually at war with each other. Among these was one called the Sultan of Persia, and another of Babylon. The former being worsted, called in the Turks to his assistance. They sent him an auxiliary army of only three thousand men; and from this slender beginning has arisen the vast empire of the Ottoman Porte. The three thousand men were commanded by a general called by the Greeks Tangrolipix, and by the Asiatics Togrul Beg. Being a man of ability, the Sultan of Persia, by his assistance, got the better of his adversary; but, refusing to let the Turks depart, Tangrolipix with his army withdrew to the desert of Carbonitis, where, being joined by numbers of discontented Persians, he began to invade the territories of the Saracens. The Sultan of Persia sent against him an army of twenty thousand men, whom Tangrolipix surprised and defeated, acquiring at the same time an immense booty. The fame of his victory, and his wealth, procured him bands of robbers, thieves, and blackguards, from all the neighbouring countries; so that he soon found himself at the head of fifty thousand. Against such a formidable force the Sultan of Persia marched in person; but happening to lose his life in the engagement by a fall from his horse, his men threw down their arms and acknowledged Tangrolipix to be Sultan of Persia.

The new sultan instantly thought of destroying other sultans and potentates; for which purpose he opened a passage for his countrymen from Armenia to Persia. The Sultan of Babylon was the first victim; after which Tangrolipix turned his arms unsuccessfully against the Arabians, but afterwards more successfully against the Greek emperors. The first invasion by the Turks took place in 1041; and in four hundred and twelve years they became absolute masters of the empire. Though unsuccessful at first against the Saracens, they prevailed greatly afterwards, and, by the time of the crusades, we find them masters of Palestine, as well as several other countries formerly conquered by the Arabs. From the time of their first invasion, in 1041, we may say, the war never ceased; and there is the greatest reason to suppose that the Greek empire would have been overthrown in a very short time, had not the crusaders checked their progress. The immense numbers with whom the barbarians had now to contend (amounting to no fewer than seven hundred thousand) threatened with destruction the newly erected empire of the Turks; and had it not been for the want of unanimity among the crusaders themselves, and the jealousy of the emperors of Constantinople, they certainly would have overthrown it. But, as matters went, all their labour was lost; and they only increased the general carnage and desolation to an extreme degree. The first crusade was planned in 1093, published in 1095, and in March 1096 the first army set out. In 1097 they began their conquests, but soon found it very difficult to keep them. The Turks being at home, and united, had many advantages over foreign invaders; which the latter endeavoured to counteract by drawing continual supplies of fresh men from Europe. Thus, for several centuries, the western part of Asia was rendered a scene of bloodshed and desolation. When they had contended for something more than two hundred years, Jenghiz Khan, the Mogul, seems to have formed the noble design of destroying the whole human race at once, excepting only his own immediate followers. His plan was, to exterminate man, woman and child wherever he went, and to plant the countries with his own people. It is impossible to do justice to his exploits. Voltaire, speaking of the irruption of the Moguls, says, that the people fled every where before them, like wild beasts roused from their dens by other beasts more savage than themselves. In the Universal History we are told, that he is supposed to have destroyed fourteen millions and an half of his fellow creatures. He died in 1227, and left successors worthy of himself. Some of these proceeded eastward, and some westward. The latter, under the conduct of a monster named Hula-ku, overthrew, in the year 1256, the remains of the Saracen empire, by the taking of Bagdad. The miserable Khalif, coming forth to meet his conqueror, was trampled under his horse’s feet, then sewed up in a sack, dragged through the streets, and thrown into the river. The Moguls who proceeded eastward invaded China. The Chinese resisted with innumerable multitudes, and battles were fought to which those of the present age are mere skirmishes. The soldiers, overcome with thirst, drank blood instead of water; hundreds of thousands fell on both sides, while human blood ran in streams for five or six miles. At last the fury of the Moguls was stopped by the ocean; for, having attempted the conquest of Japan, their fleet was wrecked, and an hundred thousand perished. Like other great empires, also, pretenders to the sovereignty started up, and the whole was parcelled out into a number of little states, which, of course, ceased to be formidable.

The decline of the Mogul empire did not restore peace to the world. The Turks continued their ravages; the western nations continued their crusades. England, which became a kingdom in 800, had been ravaged and conquered by the Danes and Normans, and likewise distressed by civil wars. At last, having emerged from its own difficulties, it began to inflict upon other nations the miseries itself had endured. Wales and Scotland became objects of the ambition of Edward I, who had already signalized his valour in the crusade. The Welsh were totally subjugated, and the Scots overthrown in the very bloody battle of Falkirk, where almost the whole force of the country was destroyed. The Scots, however, were never totally subdued. Robert Bruce retaliated on the English in the battle of Bannock-burn, where two hundred thousand English were defeated by thirty thousand Scots. But Robert was not contented with asserting the liberty of his country. Jealous of his brother Edward, he sent him with an army to conquer Ireland. We shall not doubt of his valour, or of the miseries he inflicted, or was willing to inflict, upon the people among whom he came. In destroying them he destroyed his own army. They were reduced to the most dreadful straits by famine, insomuch that they were obliged to feed upon the most loathsome matters, their own excrements not excepted.

Being now arrived at the beginning of the fourteenth century, we see that, from Ireland to China, mankind had involved themselves in one general work of destruction. Besides the wars, famines had been so frequent, that the eating of one another seemed to be but a common affair. Indeed the history of mankind would tempt one to believe that they thought themselves brought into the world for no other purpose but to destroy each other. As far back as the year 409, in the time of the wars of the Vandals in Spain, a dreadful famine took place, which, in 410, reduced many to the necessity of feeding upon human flesh; parents devoured their children, and the wild beasts, being deprived of the dead bodies which they used to feed upon, but which were at this time devoured by the living, fell upon the latter, and thus increased the general destruction. Such of the Romans as fled into strong holds and fortresses, were in the end obliged to feed upon one another. To these calamities the pestilence was added, which did not fail to rage in its usual manner. Famine and pestilence had also ravaged the city of Rome when besieged by the Goths under Vitiges, and under Totila. In this last siege the unhappy citizens were reduced to such straits, that they consumed even the grass which grew near the walls, and were at last obliged to feed on their own excrements. We do not indeed hear, at this time, of any particular instances of people feeding upon one another; though, in such dreadful emergences, it is scarcely to be doubted that some would have recourse to this terrible expedient in order to allay their hunger. But in the famines which took place during the ravages of the Saracens, Turks and Moguls, nothing seems to have been more common. In 1066 a most grievous famine took place at Alexandria in Egypt, and throughout the whole country. Three bushels and a half of flour were sold at eighty dinars, a dog at five, and a cat at three. The Visir, having waited on the Khalif, left his horse at the palace gate; but, before he returned, the animal had been carried off and eaten. Three men were hanged for this theft, and their bodies ordered to be exposed upon gibbets; but next day they were found picked to the bones, their flesh having been all cut off and devoured the preceding night. Bodies of men and women were boiled, and their flesh publicly sold. A violent plague followed, which swept away the greatest part of the inhabitants. As the hellish Moguls spread desolation wherever they advanced, so their retreats were equally formidable. In 1243, having advanced as far as Aleppo in Syria, they found themselves obliged to retreat, and that for a very odd reason, viz. that their horses were not well shod. This, however, did not hinder them from destroying every thing the earth produced, and stripping every man, nay, every woman, they met, even of their clothes. The consequence was, a terrible famine, so that people were fain to sell their children for small pieces of bread.

Such was the conduct of men, from one end of the earth to the other, during the interval, if any interval there was, between the plague in the time of Justinian and that of 1346. The pestilence, which had continually raged in one place or other, now overspread the whole world. At what time it began to decline we know not; and, indeed, as the same desolations and massacres continued, if these had any share in its production, it ought scarcely to have declined at all. That there was all this time little or no interval, appears from what Dr. Rush says, vol. iii. p. 165, that between the years 1006 and 1680, that is, in a period of 674 years, the plague was fifty-two times epidemic all over Europe. Supposing the intervals between every general infection then to have been equal, and the plague to have lasted only one year at a time, it must have recurred once in twelve years. But the intervals were not equal; for the Doctor tells us that it prevailed fourteen times in the fourteenth century; which gives an interval of less than seven years; and if the pestilence so frequently overspread the whole continent, we may be very sure that it never was out of particular places of it. The Doctor adds, “The state of Europe in this long period is well known.” We shall also consider that of Asia.

The empire of the Moguls, which had fallen into decay, revived under Tamerlane; who, following the example of Jenghiz Khan, had the epithet of the destroying prince bestowed upon him by the Indians, on account of his behaviour in their country. Building his captives into walls with stones and lime, pounding them by thousands in large mortars, was his common practice; while the Turks, proceeding westward, wasted every thing with fire and sword; the christians all the while continuing their mad crusades, and when driven from one place endeavouring to establish themselves in another. At last the Turks and Tartars, or Moguls, or rather their emperors, happening to quarrel, the battle of Angora, in Galatia, decided (at the expense of some hundred thousand lives) the dispute in favour of Tamerlane; but, as his empire ended with his life, the Turks soon recovered from the blow they had received; and, by the taking of Constantinople in 1453, put an end to the terrible commotions which had prevailed in the east for so many ages. The crusades had also for some time been discontinued, and the world hath since that time been comparatively in a state of peace.

But, by so much intercourse with the Asiatics, especially with the countries particularly subject to the plague, all Europe had been so deeply infected, that the distemper could not but prevail for a long time, even though it had not been kept up by the almost continual wars of the Europeans with one another, which was too much the case. Dr. Sydenham informs us that before his time the plague commonly visited England once in forty years; but by this we must understand a very violent infection; for Dr. Rush tells us that plagues prevailed in London every year from 1593 to 1611, and from 1636 to 1649. The author of the Journal of the Plague Year (1665) mentions a visitation in 1656; and Mr. Carey, in the beginning of his account of the plague of London in 1665, says, that the plague was almost continually among the diseases enumerated in their bills of mortality; so that we may fairly conclude it to have been endemic in that city. Now let us see how England had employed itself. Its kings, as well as many of their subjects, had gone to the holy wars, as they called them, and, by continuing in that devoted country where most probably the pestilence first originated, it is impossible to suppose that some of them did not receive the contagion. Having caught the pestilence in the holy war, they came home to diffuse it among their countrymen, and to keep it up by profane wars, I suppose, both foreign and domestic. Henry VII put an end to a very long and bloody contest between the houses of York and Lancaster; but he brought the pestilence along with him, which raged violently during the fifteenth and sixteenth centuries. A most violent war, for half a century, on the continent of Europe, and civil wars in England, would still continue to keep the infection alive from 1600 to 1648, when a general peace was concluded; and from the subsequent state of tranquillity, probably, after the violent attack in 1665, it seems to have languished and died in England, as a plant in a soil not natural to it.

But, though England has since remained in peace, on the continent it has been otherwise. In the beginning of the eighteenth century, the heroic madness of Charles XII seemed ready to confound the north, while the glorious exploits of prince Eugene and the duke of Marlborough appeared equally confounding to France. In the midst of these grand atchievments, the pestilence silently claimed its share in the common work of destruction; carrying off upwards of two thousand in a week for some time, in 1709, in the city of Dantzick, and, in 1711, twenty-five out of sixty thousand inhabitants in Copenhagen.

The infection, however, seemed now to be retiring to the place from whence it originally came. In 1666, or soon after, it seems to have totally abandoned the island of Britain; with the attack in 1711 it left the western countries of the continent next to that island; in 1713, 1714 and 1715 we are informed by baron Van Swieten that it ravaged Austria; in 1721, or soon after, it abandoned France; in 1743 it made its last attack on Messina; and in 1784 we find it confined to Dalmatia and the eastern territories, where it has so long reigned without interruption.

From the view then which we have taken of the conduct of the human race, and the consequences of that conduct, we may reasonably conclude, that war will produce famine and pestilence, and that after all violent wars a violent pestilence may be expected, especially if the contending parties interfere with those nations where it is most frequent. Another piece of conduct by which mankind expose themselves to pestilential contagions is, the practice of cooping themselves up in great cities. Mr. Gibbon, speaking of earthquakes, says, that men, though always complaining, frequently bring mischief upon themselves. “The institution of great cities (adds he) which enclose a nation within the limits of a wall, almost realises the wish of Caligula, that the Roman people had but one neck. In these disasters (earthquakes) the architect becomes the enemy of mankind. The hut of a savage, or the tent of an Arab, is thrown down without injury to the inhabitant; and the Peruvians had reason to deride the folly of the Spanish conquerors, who with so much cost and care erected their own sepulchres. The rich marbles of a palace are dashed on its owner’s head, a whole people is buried under the ruins of public or private edifices, and the conflagration is kindled and propagated by innumerable fires necessary for the subsistence and manufactures of a great city.” In plagues, great cities are unquestionably as pernicious as in earthquakes; not indeed by reason of the weight and bulk of the materials, but the confinement of the people within the sphere of infection, and their continual exposure to the causes which prepare the body for receiving it. In fact, it has always been found that plagues begin in cities; and were it not for the multitudes that continually fly out of them there can be no doubt that the mortality would be much greater than it is. The intercourse of many nations with one another, the carrying from one end of the earth to the other of goods capable of bringing with them the infection, must also be supposed a very principal cause of pestilence; but this last will be more fully considered in the next section. At present we may conclude, that, the pestilential contagion having originally fallen upon mankind for their sins, it is still kept alive by the same causes; and, as far as we can conjecture, these sins are, the propensity to murder and destroy which breaks forth in war; the vanity, pride and luxury which produces great cities; and the same vanity, &c. joined with avarice, which gives life to commerce. Add to all this the neglect of the cultivation of the earth, which ought to be the principal business of man. In consequence of this neglect, immense tracts of it are still overrun with woods, covered with stagnant and noxious waters, or lying in waste and now uninhabitable deserts, fit only for serpents and the most destructive animals. Thus the very climate is changed from what it ought to be; the elements become hostile to man in an extreme degree, and the whole system of nature, originally designed to give life and happiness to the human race, is, through their own misconduct, changed into a system of misery, disease and death.

The account just now given of the ways in which mankind bring upon themselves the plague, and other diseases almost equally terrible, is so conformable to the opinions of the learned Dr. Mead, that I shall conclude this section with a few extracts from his works. Of the small pox he says, that he supposes this “to be a plague of its own kind, originally bred in Africa, and more especially in Ethiopia, as the heat is excessive there; and thence, like the true plague, was brought into Arabia and Egypt, after the manner above mentioned” (i. e. by war and merchandise.) “Now (adds he) if any one should wonder why this contagion was so long confined to its native soil, without spreading into distant countries, I pray him to consider, that foreign commerce was much more sparingly carried on in ancient times than in our days, especially between Mediterranean nations; and likewise that the ancients seldom or never undertook long voyages by sea, as we do. And Ludolfus observes, that the Ethiopians in particular were ignorant of mercantile affairs. Therefore when in process of time the mutual intercourse of different nations became more frequent by wars, trade and other causes, this contagious disease was spread far and wide. But, towards the end of the eleventh century, and beginning of the twelfth, it gained vast ground by means of the wars waged by a confederacy of christian powers against the Saracens, for the recovery of the Holy Land; this being the only visible recompense of their religious expeditions, which they brought back to their respective countries.” Of the true plague he says, “It appears, I think, very plainly, that the plague is a real poison, which, being bred in the southern parts of the world, is carried by commerce into other parts of the world, particularly into Turky, where it maintains itself by a kind of circulation from persons to goods; which is chiefly owing to the negligence of the people there, who are stupidly careless in the affair: that, when the constitution of the air happens to favour infection, it rages there with great violence; that at that time, more especially, diseased persons give it to one another, and from them contagious matter is lodged in goods of a soft, loose texture, which, being packed up and carried into other countries, let out, when opened, the imprisoned seeds of the contagion, and produce the disease whenever the air is disposed to give them force; otherwise they may be dissipated without any considerable ill effects. The air of our climate is so far from being ever the original of the true plague, that most probably it never produces those milder infectious distempers, the small pox and measles. For these diseases were not heard of in Europe before the Moors had entered Spain; and, as already observed, they were afterwards propagated and spread through all nations, chiefly by means of the wars with the Saracens. The sweating sickness was most probably of foreign original. It began in the army with which king Henry VII came from France, and landed in Wales; and it has been supposed by some to have been brought from the famous siege of Rhodes, three or four years before, as may be collected from one place of what Dr. Keyes says in his treatise on the disease. We had here the same kind of fever in 1713, about the month of September, which was called the Dunkirk fever, is being brought by our soldiers from that place. This, probably, had its original from the plague which broke out at Dantzick a few years before, and continued some time among the cities of the north.”

I now take leave, for the present, of this subject, which exhibits the conduct of mankind in such a disagreeable view. Some, like M. Millot above quoted, may be apt to suppose that many of the accounts are exaggerated. But it is evident, that in our days it is impossible to determine any thing to be a falsehood, said to have happened in former ages, which is not absolutely contradictory to reason. Every one of the accounts inserted in this section has found a place in the works of historians reckoned authentic, particularly in the Universal History. All who believe the New Testament must certainly believe, from the words of our Saviour, that extraordinary things were to happen in the ages subsequent to his appearance. Can we then discredit the relations of those historians who inform us that extraordinary things have happened? Modern historians, making their own judgments the infallible measure of wisdom, and the strength of nations now existing the ultimate measure of human power, have endeavoured to turn into ridicule every thing which does not precisely accord with these two. In this the French are particularly culpable; accounting every thing to be incredible which exceeds the power of modern France to accomplish, though they certainly do not know even the extent of this power. Of such scandalous vanity we have a notable instance in the works of president Goguet, who positively determines that the walls of ancient Babylon, the pyramids of Egypt, and all the wonderful works of Semiramis, Nebuchadnezzar, &c. were not equal to the canal of Languedoc made by Louis XIV!

SECTION III.

Of Disease in general.—The nature of the Plague as a Disease considered.—Of Contagion.—Whether the Plague is really Contagious or not.—Medical History of the Distemper.—Inquiry into its Immediate Causes, and whether an approaching Plague is indicated by any visible Signs.

HITHERTO we have considered the origin of the plague entirely in a moral point of view. We have seen, that, in conformity to the general opinion of mankind, it may reasonably be supposed to have been inflicted upon mankind, the Jews particularly, for their transgressions; that, having been once introduced, it has been perpetuated, and spread from nation to nation, and that in proportion to the degree of immorality of a certain kind prevailing through the world. From this it is naturally to be inferred, that, were the human race to live at peace with one another, to disperse themselves over the face of the earth for the purpose of improving it by cultivation, and were they to be contented with what the produce of each country affords, there would be no plague among them. But we know that such a reformation is not to be expected, and we must take the world as we find it. The question then is, By what means shall individuals secure themselves from being destroyed by a plague which shall happen to invade any country; or how shall a person, already infected with it, be restored to health? For this purpose let us begin with considering the nature of disease in general, and of the plague particularly.

As to disease in general, physicians have differed very considerably in their definitions; and, though many have been given, few seem to be unexceptionable. That of Dr. Fordyce seems to be among the clearest and most expressive. “Disease (says he) is such an alteration in the chemical properties of the fluids or solids, or of their organization, or of the action of the moving powers, as produces an inability or difficulty of performing the functions of the whole or any part of the system, or pain, or preternatural evacuation.” But as this definition, however just, cannot be easily understood by such as are unaccustomed to medical language, I shall attempt the following explanation of the animal economy, and the diseases to which it is subject.

1. By nature our bodies are formed of certain solid and fluid parts, operating upon one another in a manner of which we know but little. Anatomists have described the structure of the human body and its parts in a certain degree, but have always found themselves lost in an inconceivable minuteness of texture. The whole structure of the human body, visible and invisible, is called its ORGANIZATION.

2. This organized body is acted upon by certain powers residing in the atmosphere, by which it becomes endowed with LIFE.

3. The operation of those powers upon a well organized body constitutes that agreeable and vigorous state which we call HEALTH.

4. The operation of any other power, substituted in place of the natural one, even upon a body perfectly organized, produces a state very different from health; commonly attended with some uneasy sensations, and which is called DISEASE. I say it is commonly attended with uneasiness, but not always; for many persons within a few hours, nay, a few minutes, of their death, have imagined themselves quite recovered and well. To illustrate the meaning of what is said of the substitution of any power instead of the natural one: It is natural for man to breathe air of a certain quality; and while he does so he continues in health; but let him breathe the vapour of burning charcoal, or of fermenting liquor, mixed in considerable quantity with the air to which he has been accustomed, and he will very soon find himself diseased. Many other kinds of elastic fluids may be substituted instead of the vapour just mentioned, all of which will in a short time produce a disease in the most healthy man. The state of a diseased body being very different from that of a sound one, the appearances are consequently very different. The various appearances of disease in the human body are called symptoms of that disease, from a Greek word signifying appearance.[44]

5. A disease proves mortal only by the DISORGANIZATION of the body. By disorganization I mean any considerable alteration in the structure of the body, visible or invisible. The truth of this will appear from a consideration of the method by which animals may be recovered, after being to appearance dead by breathing the vapour of charcoal, or fixed air in any other form, viz. by plunging them in cold water. In a cave in Italy a continual stream of this kind of air issues from the ground. It rises but a small way, so that a man may safely enter, because his head is above the vapour; but, if he brings a small dog with him, the animal, in consequence of breathing the pernicious fluid, falls down as if dead, and would very soon die if left there. By throwing it into a lake in the neighbourhood, (cold water of any kind would answer as well) it recovers. In the dissection of some unfortunate people, who have been killed by breathing this pernicious fume, a manifest disorganization has been observed, viz. a rarefaction of the blood, and too great dilation, or even rupture, of the small vessels.

6. A disease cannot always be cured by removing the cause which brought it on: it is necessary also to repair the injury done to the organization. This is exemplified in the case of the dog just mentioned. Taking him out of the vapour is not sufficient for his recovery, because the organization of the body is injured; the cold water by contracting the vessels repairs the injury, and the cure is completed. To the entire preservation of this organization it is probably owing, that people have frequently recovered after being thought dead for a long time.[45]

7. When the organization of the body is injured, the action of the natural powers themselves occasions uneasiness, and increases the disease. The cure then is, to substitute instead of the natural power, as far as possible, the action of some other power till the organization is restored; after which the natural power must be again allowed to act, or a disease of another kind will take place. This may be exemplified in a consumption of the lungs; where, that part being very much disorganized, pure air renders the disease worse; and the sick are relieved by mixing with the common atmosphere such kinds of air or vapour as would prove pernicious to people in health. But, supposing this method to be successful, and the consumption to be entirely removed, it is plain that the use of the pure atmosphere must be resumed, or the impure air would bring on a disease in the same manner as on a healthy person.

8. The body is wasted in the natural operations of life; part of it passing off with the vapour of the breath, part by insensible perspiration, &c. Hence it naturally tends to disorganization and death, unless the waste be repaired.

9. This natural waste of the body is repaired, and health kept up, by the food and drink taken into the stomach.

10. Hence arises another set of diseases; for as the reparation of the waste, just mentioned, depends on the proper action of the stomach upon the food, and the assimilation of the latter with the substance of the body, it is plain that this operation depends both on the proper quality of the food, and the sound state of the stomach itself.

11. The body is composed of solids and fluids of different kinds, every one of which is subject to diseases peculiar to itself; but, by reason of the connexion of the parts of the body with one another, it is impossible that any one can be very much disordered without affecting all the rest. As the bond of connexion, however, is in many cases totally invisible to us, surprising instances frequently occur of one part being affected in consequence of an injury done to another very distant from it. This connexion between all parts of the body is called SYMPATHY. Dr. Gardiner of Edinburgh, in his observations on the animal economy, &c. says, that “the stomach is the principal seat of many of the most remarkable sympathetic affections which happen in valetudinary states of the body. Every disorder accompanied with severe pain affects the stomach, whilst this viscus affects not only in its diseased state every part of the system, but at other times the effects of healthful stimuli applied to it are instantly communicated to the rest of the body, as when we take food, wine, or medicine.” Dr. Darwin in his Zoonomia informs us that the stomach is said to sympathize with almost every part of the body; but Dr. Moore, in his medical sketches, tells us that the heart possesses a greater share of sympathy than any other part in the body, and next to it the stomach.[46]

12. The solid parts of the body are the bones, the muscles, brain and nerves; the fluids are, the blood, and others produced from it. The bones are known to every one; the muscles are the fleshy parts throughout the whole body; and the nerves are a kind of cords seemingly originating from the brain, and from thence accompanying the blood vessels through all parts of the body.

13. Much has been disputed about what is to be accounted the primary part of the body, on which all the rest depend; and one class of disputants have arranged themselves on the side of the blood, and the other on that of the nerves. The dispute is like one about the beginning of a circle. It cannot be decided, because the blood cannot act without nerves, nor the nerves without blood. I speak of the human body, being aware that in some animals the position may be controverted. The following is a concise state of the matter.

14. All the blood in the body passes through the heart; which has four cavities; two called ventricles, and two auricles. These, from their position in the body, are called the right and left. The right ventricle communicates with the right auricle, as does also the left ventricle with the left auricle; but there is no communication between the right ventricle and the left, nor between the right auricle and the left. Through these cavities all the blood passes to every part of the body, and returns from every part; but, as in the former case, we are here at a great loss where to begin its motion; for this is precisely to find the beginning of a circle. As we must begin somewhere, however, we shall do so with the right ventricle of the heart. This receives the blood returning from all parts of the body, and propels it into the right ventricle; not the whole quantity at once, for it cannot contain one half of it; but by degrees. The auricle contracts as soon as it is full; and in the time that the auricle fills, the ventricle contracts, so that it may be empty, and ready to receive the blood from the auricle. By the contraction of the right ventricle the blood is driven into the pulmonary artery, and passes into the lungs. Here the artery branches into an infinite number of small vessels much finer than hairs; and these again, uniting into larger trunks, form at last the pulmonary vein, which brings back the blood to the heart. The pulmonary vein is inserted into the left auricle of the heart, which, as soon as it is filled with blood, contracts, and expels the blood from it into the left ventricle. From the left ventricle issues a large artery called the aorta, which by its branches supplies the whole body with the vital fluid. In all parts of the body the arteries divide themselves into innumerable small branches, which terminate in veins equally small as in the lungs; but it has been disputed whether the arteries and veins actually join each other in the form of vessels, or whether the arteries deposit the blood in small cells, from which the veins suck it up. The dispute is of no consequence, nor can it be absolutely decided, on account of the exceeding smallness of the vessels; though the microscopical observations are rather favourable to the opinion of a continuation of vessels. The veins from all parts of the body unite into larger vessels, and these again uniting with one another, form at last one very large vein called the vena cava, which opens into the right auricle of the heart, from which the circulation goes on as already described. The two ventricles of the heart, and all the veins throughout the body, are furnished with a kind of valves, which allow the blood to proceed in the way of circulation, but prevent its returning in a contrary direction.

15. The lungs, through which all the blood in the body passes, receive likewise the air which we draw in every time we breathe. They consist of two large bodies called lobes; from their situation called the right and left. The air is conveyed into them by the wind-pipe, called also the trachea, and the aspera arteria. On entering the cavity of the breast, the wind-pipe divides into two large branches called the bronchiæ; one of which goes to the right and the other to the left lobe of the lungs. By the further division and subdivision of these vessels the lungs are filled with an innumerable multitude of little tubes, terminating in exceedingly minute bladders or cells, which are the final receptacles of the air sucked in when we breathe. Each of these cells is surrounded with a kind of network of blood-vessels exceedingly small, and consisting of very thin membranes; so that, in passing through the lungs, the blood is exposed as much as possible to the action of the air.

16. It is a matter of great importance to find out what is the use of this exposure of the blood; and great disputes have taken place concerning it. In former times it was supposed that the blood received from the air a vital spirit, without which it would have been totally incapable of performing its offices in the body. Later physiologists endeavoured to explode this notion. Dr. Hales particularly, by shewing that the circulation of the blood through the lungs might be continued by inflating and contracting them alternately by the fumes of burning brimstone, endeavoured to prove that the use of the air was only to give the lungs an opportunity of dilating and contracting alternately, by which means principally he thought the circulation might be carried on. This continued to be the most common hypothesis as late as the time of Dr. Huxham. It was however thought also that by the compression of the air the blood was altered in its texture, its bulk, &c. Accordingly Dr. Huxham tells us in the preface to his treatise on air and epidemic diseases, that “air fit for respiration ought neither to be too hot, nor very cold; for the use of the inspired air is to temperate the blood, which would otherwise grow too hot, and putrefy, as is evident from the experiment of the most excellent Boerhaave made in a hot house; for, if the air is more hot, or even equally hot, as the blood of any animal, it certainly soon dies.”[47]

17. The modern discoveries in the composition of air, have tended greatly to elucidate the use of this fluid in the lungs, and its action on the blood in respiration. Dr. Priestly first determined it to be what he terms a phlogistic process, i. e. a process by which the parts of the blood no longer proper to be retained among the rest, or at least some of them, are carried off. That something is carried off either from the lungs themselves, or from the blood circulating through them, is evident; for the air which is taken into the lungs in a dry state, comes out of them extremely moist, and loaded with vapour. An essential change is also made in the nature of the air itself; for it now assumes in a great measure the nature of what has been called fixed air, or the fume of charcoal, or fermenting liquor, and thus becomes unfit for being breathed a second time. This change is made by the addition of some terrestrial substance to the pure atmosphere, which the latter volatilizes and carries along with it.[48]

18. But, whatever may be carried off from the blood, during its passage through the lungs, something is certainly added to it, for the blood in the pulmonary artery is of a dark red, but when it has undergone the action of the air in the lungs, and returns by the pulmonary vein, it is then of a bright scarlet, which colour it retains through all the arteries of the body, but loses it on its return through the veins. This scarlet colour is communicated to blood in all cases when exposed to the air; and Dr. Priestley has observed that it is acted upon by the air even through a bladder; much more then must it be so through those very thin membranes which form the coats of the fine pulmonary vessels. What this subtile matter is which the blood receives, shall be afterwards inquired into; at present it is sufficient to take notice that it is absolutely necessary, for the purposes of life, that the blood should pass through the lungs: for, as Dr. Huxham observes, “we see neither nutrition, nor the motion of the muscles, performed by any blood that hath not passed through the lungs; this is observable from the coronary arteries[49] to the ultimate ramifications of the aorta.” As the previous circulation of the blood through the lungs therefore is absolutely necessary to the growth and life of the body, and as the blood certainly receives something from the air, we must account this a proof, and no inconsiderable one, that the air contains a vital spirit, which it imparts to the blood in the lungs. But, before we proceed farther on this subject, it is proper to take some notice of

19. The nerves. These, which constitute such a remarkable and important part of the human body, are white cords, of a soft pulpy substance, defended by a tough skin which goes along with them as far as they can be traced. All the nerves either originate from the brain, or terminate in it. The former doctrine hath been generally adopted, and in conformity to that doctrine the following account of the nerves is laid down. The brain is enclosed in the cavity of the scull, but not without the intervention of two membranes, called the dura and pia mater, to prevent injury from the hard bones, as well as for other purposes. The brain is divided into two lobes, the right and left. It is composed of two different kinds of substance, the outermost called the cortical, the innermost the medullary substance; the latter seems composed of fine fibres. The whole of the medullary part of the brain terminates in a substance called the cerebellum, very much resembling the brain, but smaller. The cerebellum terminates in another substance resembling the medullary part of the brain, called the medulla oblongata. The cerebellum lies in the back part of the head, and the medulla oblongata under it. The latter terminates in the spinal marrow, extending from the lower and back part of the head to the lower extremity of the back bone, and is enclosed in the hollow of that bone. The nerves proceed from these four substances, viz. the brain, the cerebellum, the medulla oblongata, and spinal marrow. As they pass to all parts of the body they accompany the arteries, dividing with them into innumerable small branches; but they do not return with the veins; so that they seem not to contain any fluid which goes and comes, or which circulates like the blood. The nervous fluid, if any such there be, seems to move constantly one way, either to the brain or from it.

20. Hitherto we have noticed only things which are evident to our senses, and which the industry of anatomists has abundantly evinced; but now our subject renders it necessary to step aside a little into the obscure regions of theory and conjecture. The muscles, as we have formerly said, are the fleshy parts of the body; and by them all the motions of the body are performed. The flesh is distributed into distinct portions, each of which is enclosed in a membrane belonging to itself. Each of these portions is a muscle, and each muscle has a branch of an artery and the branch of a nerve belonging to it. On both these the action of the muscle depends; for, if we cut the nerve belonging to a muscle, it immediately loses all power of action; and if we cut the artery which accompanies the nerve, it does the same. As therefore the blood is found to receive something from the air, and as it loses this when passing through the arteries, and as the nerves lose their power when the communication with the blood is cut off, it seems extremely probable, that what is imbibed by the blood in the lungs is taken up by the fine ramifications of the nerves, and is no other than the immediate principle of life and sensation. Thus we will establish a doctrine directly opposite to that commonly received; for, instead of supposing that the nerves originate from the brain, we are now led to suppose that they terminate in it. Instead of supposing that the sensations originate in the brain, we will be led to suppose that every sensation originates in the organ appointed for that sensation. Thus we are conscious that our eyes, not our brain, are the parts of our body which immediately perceive the light; our fingers, or any other parts of the body, feel what is applied to them; and of consequence we have reason to believe that the animal spirits, nervous fluid, or whatever we please to call it, proceed from the surface of the body inwards to the brain, not outwards from the brain to the surface of the body. The brain itself seems to resemble a large collection or reservoir of water, in which the sensations, like so many small streams from every part of the body, unite, and in which our intellectual faculties reside in a manner totally inexplicable by us. Thus far it seemed necessary to theorise, in order to form some idea, however obscured, of the connexion between the nerves and our sensitive and intellectual, or, if we please to call them so, our spiritual faculties.

21. In consequence of this very intimate connexion between the blood and nerves, it is easy to see that any injury done to the one may very greatly affect the other; and that a very slight, nay, to us imperceptible, change in the organization of either, may produce the most grievous, and even incurable disorders throughout the whole body, or in any particular organ. Let us now consider a little farther the blood-vessels.

22. It hath been a question, whether in the structure of these vessels nature hath observed an exact proportion. For instance, if the blood passes by a kind of starts through four cavities, as we are assured that it does, it seems natural to suppose that these four should be exactly equal. This, however, hath been denied; and some, from its accommodating the human frame to their theory, have fancied that they saw the use of such disproportionate work. Dr. Huxham expresses himself in the following words: “Nor doth the air only refrigerate the blood, but, by preventing its too great ebullition, and condensing it, hinders it from bursting the vessels. This indeed is of exceeding great importance, if, with the very learned Helvetius, we suppose the capacity of the right ventricle of the heart to be greater than that of the left, and that the pulmonary arteries are larger than the correspondent veins; for it thence follows, that the blood ought to be considerably condensed by the inspired air, that an equal quantity of blood may be received, in one and the same time, by the pulmonary veins and left ventricle of the heart, that is thrown off from the right ventricle, and through the more capacious pulmonary arteries. This indeed many deny, asserting quite the contrary. It is necessary, however, that the aorta should receive as much blood from the left ventricle of the heart, as is thrown off from the right ventricle through the pulmonary artery; and that in the very same and equal time, or a fatal deluge would soon overwhelm the lungs, because the contraction of each ventricle is made at one and the same time; we always find therefore the aorta and pulmonary artery, in a natural state, equal on this account; also the capacity of the ventricles ought to be equal, that they may receive, in one and the same space of time, equal quantities of blood,” &c.

If any thing farther is necessary upon this subject, we may still observe, that if the blood were at all condensed by the air, it would be so unequally, because the air is at some times much colder than at others; and thus the disproportion of the cavities of the heart to one another could not fail of producing the most disagreeable if not fatal effects. We often see what terrible consequences ensue upon the enlargement of any part of an artery near the heart; and these would, sometimes at least, be felt by every individual.[50]

It is true, indeed, that this objection will in some degree hold, even though we suppose all the cavities of the heart to be equal, and the capacities of the blood vessels to be perfectly uniform throughout the whole body. For, if we suppose the blood to be at all condensed in the lungs by the coldness of the atmosphere, it must undoubtedly follow, that while passing from them it occupies less space than before it arrives at them. Hence the pulmonary vein, the left auricle of the heart, the left ventricle, the aorta, and all the rest of the arteries for a considerable way, must be comparatively empty, even though they receive as much fluid as fills the vena cava, right auricle and ventricle of the heart, and pulmonary artery. The equality which ought to prevail in the system, and which indeed cannot be dispensed with, can only take place in those remoter branches of the arteries in which the blood has reassumed its former state of dilation or rarefaction.

23. If we consider this matter attentively, we shall find it not a little mysterious. Every time we breathe out the air we have sucked into our lungs, a considerable quantity of moist vapour is breathed out along with it; but it has been proved by undeniable experiments that the emission of aqueous vapour from any substance cools it in proportion to the quantity of vapour emitted. Every breath we draw, then, cools the lungs, and consequently the blood, to a certain degree, and, as the number of times that we breathe in a day is exceedingly great, the cold produced by the evaporation ought to be in proportion. But we see that, notwithstanding all this cooling, whether we breathe cold air or hot air, the temperature of the body remains still the same. The air then, though constantly carrying off the heat of the body, does not cool it in the least by its action on the lungs. The only possible way of solving this apparent contradiction is, by supposing that the air, when acting upon the blood in the lungs, leaves precisely as much heat as it carries off, and therefore, though we breathe ever so long, we cannot by this means become either hotter or colder.

24. To illustrate this subject, we might now enter into an inquiry concerning the origin and cause of animal heat; but this will be touched upon hereafter. We shall here only take notice that the heat of the body is almost universally allowed to proceed from the lungs. It has likewise been demonstrated, that the air does in fact contain an incredible quantity of heat, even when it appears to us to be extremely cold. A certain proportion of this heat is separated from it every time we breathe; and if, either by the mixture of other fluids with the air we breathe, or by any change in the organization of the body itself, a greater or smaller proportion of heat should be communicated to the blood, disease must ensue.

25. To sum up then what has been said concerning the blood and nerves: The whole mass of fluid passes from the right side of the heart to the lungs. In the lungs it receives from the air something[52] necessary to the functions of life and sensation, and purifies itself from those matters which might prove pernicious. From the lungs it passes to the left side of the heart, and thence through the whole body. In its passage through the body, it is accompanied with nerves, which, taking up from the arterial blood that vital spirit received from the air, convey it to all the organs of motion, of sensation, and to the brain, where the whole powers of perception being united form our intellectual faculties, and, as far as our senses can perceive, the human spirit itself. The blood, thus deprived of its spirit, is collected from all parts of the body by the veins, and returned to the right side of the heart, from whence it is again sent to the lungs, and the process carried on as before. This hypothesis concerning the peculiar function of the nerves I first inserted in the Encyclopædia Britannica, second edition, under the article Blood, in the year 1778. It has been since continued in the third Scots edition, and from thence into the Irish and American editions.

26. It has already been observed, that the body is subjected to a continual waste. One source of this waste is the breath, by which a considerable part passes off in vapour. A great quantity also passes off by the pores of the skin; frequently in a perceptible liquid called sweat, but oftener in an invisible vapour from all parts of the body, called insensible perspiration. The latter has been thought to be the great source of waste to the human body; and it is certain, that if any person in health be weighed when he rises in the morning, he will be found considerably lighter than when he went to bed. The loss of weight in this case proceeds not only from the pores of the skin, but from the lungs; but though physicians have made a general allowance for both these, I have not heard of any experiment by which we can determine how much passes off by the one, and how much by the other, nor indeed does it appear easy to make such an experiment. Galen plainly overlooks the perspiration from the lungs entirely. “This excrementitious vapour (says he) is expelled through small orifices, which the Greeks call pores, dispersed all over the body, and especially over the skin, partly by sweat, and partly by insensible perspiration, which escapes the sight, and is known to few.” Sanctorius, and the succeeding writers, have classed both together indiscriminately; allowing the discharge to be so great, that if eight pounds of aliment be taken in, five of them pass off in this manner. In a system of anatomy, published at Edinburgh in 1791, the author says, that the discharge by the skin “is even much larger than this (the discharge from the lungs we may suppose) since it not only throws off a quantity of the aliment, but likewise what is added to the blood by inhalation, which, entering often in a very considerable quantity, is thus again expelled.” The same author likewise says, that the “perspirable matter from the skin is principally water,” and that it issues in such quantity as to be seen in subterraneous caverns evidently flying off from the surface of the body like a dense vapour. But other physiologists, particularly Dr. Blumenbach, inform us, that the matter of insensible perspiration is quite similar to the discharge from the lungs, particularly containing a great quantity of fixed air. The same account is given in Chaptal’s chemistry, on the authority of Messrs. Milly and Fouquet. This may be looked upon as a valuable discovery, especially in conjunction with that related by Drs. Beddoes and Girtanner, viz. that the flesh of animals contains a quantity of oxygen. Dr. Girtanner obtained a quantity of this air from the raw flesh of animals, and says that it may be repeatedly obtained by exposing the flesh to the atmosphere, and distilling with a heat of 60 or 70 degrees of Reaumur’s thermometer (something below that of boiling water.) Hence it is natural to conclude, that, as the discharge from the lungs purifies the blood from its useless parts, so does the insensible discharge from the skin purify the solid parts from those particles which are no longer useful. The probability of this also becomes greater by considering, that in diseases, when the quantity of matter to be thrown off is very great, the skin becomes foul, the teeth furred with black sordes, &c. all which disappear as soon as the quantity of the offensive particles is reduced to its natural standard. As to any considerable quantity of aqueous vapour being discharged this way, unless in case of sweat, it does not seem probable; for in such a case our clothes would always be moist; and in the night time the accumulation of moisture would certainly be perceptible. The sweat is entirely of a different nature from the insensible perspiration, and blood and even sand has been known to issue through the skin along with it. (See the Anatomical System above quoted.)

27. This very considerable waste of the body is repaired by the aliment taken into the stomach. In the mouth it is mixed with a considerable quantity of the liquid called saliva, and in the stomach with another called the gastric juice, with which that organ always abounds. From the stomach it passes into the intestines, where it is mixed with other two fluids; one called the pancreatic juice, the other the bile. This last is of a yellow colour, and is sometimes produced in enormous quantities, insomuch that Dr. Wade, in his account of the fevers in Bengal, mentions some patients who have voided by stool half a gallon of bilious matter in one day.

28. In the stomach principally the aliment undergoes a certain change called digestion, by which it becomes capable of being converted into the substance of the body. Much has been inquired and disputed, to no purpose, about the nature of this change, and how it is effected. One party has declared for attrition; a second for putrefaction; a third for heat; a fourth have supposed that our meat was digested by chewing; as if, like the lobster, people had teeth in their stomach! and, lastly, some learned moderns, after much pains and trouble, have found out that it is digested by solution. Dr. Moore has summed up the discoveries concerning digestion in the following words: “The food, being previously divided and blended with the saliva and air by mastication, (chewing) is swallowed, and meets in the stomach with the gastric juice, whose dissolving power, assisted by the natural heat of the place, is the principal agent in digestion. The process is completed by the pancreatic juice and bile, the nutritious parts of the food being by this process converted into chyle for the support of the body, and the grosser parts thrown out.”[53]

29. The inside of the stomach and intestines are full of the mouths of innumerable small vessels, which continually suck up from the aliment, as it passes downwards, the finer parts, in form of a white liquid, called chyle; and from the whiteness of their colour the vessels have the name of lacteals, from the Latin word lac, milk. After passing through the substance of the stomach and intestines, and running along the membrane called the mesentery, to which the intestines are attached, the lacteals unite in a large reservoir called the thoracic duct; and this again opens into a large vein on the left side, called the subclavian, which conveys the blood from half the upper part of the body; soon after terminating in the vena cava, by which the chyle is conveyed to the heart, thence to the lungs, and so on in the common course of circulation. The conversion of the chyle into blood is called the process of sanguification.

30. The blood, thus formed out of the aliment we swallow, is not one uniform fluid like water, but composed of three distinct substances; one, which gives it the red colour, and seems to be composed of little round globules; another, quite colourless, but of a viscid nature, and which very soon coagulates, called the lymph; and a third, of a yellowish colour, and retaining its fluidity much longer, called the serum. A remarkable property of this last fluid is, that air can act through it upon the blood; for Dr. Priestly found that a portion of black blood assumed a bright, florid colour from the air, even though covered with serum an inch deep. When blood is drawn, the red globules are detained by the lymph which coagulates, and both together form the red mass called crassamentum; the serum remaining fluid, and retaining its name.

31. Besides these fluids, the blood either invisibly contains, or is capable of being converted into, a great many others; for all the fluids in the body are separated from it, and all of them, the bile only excepted, from the arterial blood, before it has lost that portion of its spirit which it imbibes from the air. When a fluid is to be secreted, sometimes it is done only by an infinity of small vessels branching off from the arteries, and depositing the liquids which pass through them in particular places; and such are the fluids which moisten the inside of the body, and which are carried off by the breath, or by sweat. But this separation does not by any means hinder the artery from terminating in its usual way in a vein, for in no case is the whole substance of the blood converted into any other liquid; all of them appear to be contained in it. But the greatest number of fluids are separated by means of certain substances called glands. These are small round or oval shaped bodies; each of them enclosed in a membrane or skin which separates it from the other parts, and each furnished with a small tube called the excretory duct, through which the liquor separated in the gland passes to its place of destination. Each gland has also an artery and nerve, and a vein to bring back the blood after it has parted with the fluid intended to be separated. The bile is separated in the liver from the blood of a large vein called the vena portarum, formed by the union of some of the veins of the intestines and mesentery. This vein branches out through the liver like an artery, terminating in other veins, which at last bring back the blood to the heart.

32. As the human body is thus furnished with an apparatus for separating and carrying off, it is also furnished with one for absorbing or taking in. All the inward parts of the body are moist; and the moisture is furnished by the small vessels above described, and which separate part of the lymph from the blood. By such continual separation the cavities of the belly, breast, brain, &c. would soon be filled with liquid, were not some means provided for carrying it off as fast as it is formed. The means in question are a set of small vessels called lymphatics. These “arise from the internal surface of the breast, belly, and every cavity of the body; they also overspread the whole external surface of the body, and large lymphatic vessels are usually found close to the large blood vessels of the extremities, besides those small superficial ones which lie above the muscles in the cellular membrane (the fat or rather the membrane containing it.) The large viscera generally have two sets of lymphatics, one lying on the surface of the viscus, and the other accompanying the blood vessels belonging to it. The faculty of absorption, though refused to the lymphatics, was ascribed by many anatomists to common veins, and this opinion continued to prevail in some degree, until Hunter and Monro totally overturned it, exploding at the same time the notion that any of the lymphatics are continuations of arteries, and establishing, beyond a doubt, that all are absorbent vessels.”[54] All the lymphatics terminate in the thoracic duct; so that the liquid separated by the exhalant arteries (so the vessels are termed by which that fluid is separated) is again mixed with the blood, and again performs the same offices.

We have now taken a review of the several parts of the human body, slight and superficial indeed, but such as the limits of this work would allow, and sufficient to furnish to those entirely unacquainted with medical matters some general ideas on the subject. We have seen that the body, in general, consists principally of four great parts, the blood-vessels, the lymphatic vessels, the nerves, and the muscles. Besides these we enumerate the glands and membranes; the former being nearly allied to the blood-vessels, the latter apparently to the nerves. The bones, having no concern with our present inquiry, are not taken notice of. The stomach and intestines, being principally composed of muscular fibres, nerves, and blood-vessels, must be considered as belonging to these departments. Each of these large divisions has obtained the name of system; and even the subdivision of the blood-vessels into arteries and veins. Thus the arteries of the body, taken collectively, are called the arterial system; the veins the venous system; the brain and nerves the nervous system; the muscles the muscular system; the lymphatics the lymphatic system; and the glands the glandular system; &c. These appellations have been given for the sake of distinctness and perspicuity, but they have had a bad tendency. Insignificant disputes have arisen concerning the superiority of one system to the other, and which is to be accounted the primum mobile of the body. By observing also the general structure of the body in a more full and ample manner than that of the parts which compose it, physicians have been apt to generalize too much in their theories, and to fancy that from a few obvious laws they might be able to explain the phenomena of disease in almost every possible variety. To illustrate this, let us take the blood for an example. This to sight appears an homogeneous fluid; and Boerhaave and others have ascribed diseases to some defect or bad quality of the blood. But this fluid consists of three parts, each, as far as we can perceive, essentially distinct from the other; viz. the lymph, serum, and red globules. As each of these happens to be diseased, the cure must be different; or if two happen to be diseased, the medicines must still be varied. But, besides these general diseases arising from what, like the blood, is common to the whole body, each component part of the body has an arterial system, a venous system, a nervous and lymphatic system, &c. belonging to itself; all of which, though dependent on the body at large, have yet laws of their own, in consequence of which any one of them may be considerably diseased without much affecting the general system; and this constitutes what is called local disease. Again: The parts of the body are so connected with one another, that the disease of one may show itself in another; or it may affect the whole body in such a manner as to produce a general disease; though Dr. Rush considers this last, at least from injuries of the viscera, as a rare occurrence;[55] but we certainly know that general diseases are very often followed by evident diseases of particular organs; and in these cases it is impossible to say whether the general disease did not begin, though imperceptible to us, in that very organ in which we suppose it to terminate when the local disease was come to such an height as to be evident to our senses. In some cases it is plain that local injuries will bring on most violent diseases of the whole system. Thus a local inflammation of the end of one of the fingers, by physicians called a paronychia, has been known to induce a most violent fever, nay, even to occasion death. These violent symptoms end as soon as the suppuration is completed; so that, were it not for the excessive pain of the inflammation, we might be apt to suppose that the fever terminated in the suppuration, whereas it evidently was occasioned by the local disease, or the tendency of the part to suppurate; the pain and inflammation being necessary preliminaries. Again: When an intermittent fever is said to terminate, or to be followed, by a hardness of the liver, we do not certainly know whether an original disease of the liver might not have been the cause of the intermittent. From a consideration of all these things, viz. the extreme diversity of parts which compose the human body, the ultimate invisibility of the structure of each, the incomprehensible manner in which they are united, the equally incomprehensible dependence they have upon one another in some cases, and independence in others, the numerous laws by which they are governed, and which must be very much unknown to us, the invisible and incomprehensible nature of the powers which act upon them, &c. &c. I say, when we consider all these things, the boldest theorist must be humbled when he attempts to account for the phenomena of disease in any one instance. The excessive difficulty in which we are involved is beautifully described by Dr. Ferriar when speaking of hysterics; and obstacles equally insuperable by our theories will undoubtedly be met with in any other distemper. “We are ignorant (says he) by what laws the body possesses a power of representing the most hazardous disorders, without incurring danger; of counterfeiting the greatest derangement in the circulating system, without materially altering its movements; of producing madness, conscious of its extravagances; and of increasing the acuteness of sensation by oppressing the common sensorium. In hysterical affections all these appearances are excited, which are incompatible with the reasonings of every system-maker who has yet endeavoured to explain the inexplicable. Nature, as if in ridicule of the attempts to unmask her, has, in this class of diseases, reconciled contradictions, and realized improbabilities, with a mysterious versatility, which inspires the true philosopher with diffidence, and reduces the systematic to despair.”

Notwithstanding all these difficulties, however, physicians have theorised, and that with such animosity, as if all the arcana of nature had been laid open to every professor who thought proper to invent or new-model a system; though the constant succession of theories might certainly have shown them the vanity of such attempts. Some of these we must now consider.

Medical theorists have exerted their greatest abilities in explaining the nature of those general diseases affecting the whole body, denominated fevers; and which are likewise called acute diseases, from the violence with which they sometimes attack, and the rapidity with which they run through their course. Dr. Fordyce says, that fever will sometimes kill in five minutes from the first sensation of uneasiness. Ancient physicians have described a number of fevers, which they supposed to be of different species, and accordingly have distinguished by different names. Modern system-makers have added to the number; so that a bare detail of the names which they have given to their divisions and subdivisions, would constitute a very formidable catalogue; but the latest practitioners are decidedly of opinion that there is but one kind of fever, varying itself according to circumstances. Dr. Rush declares himself of this opinion in the most express and positive terms. “There is (says he) but one fever. However different the predisposing, remote or exciting causes may be, . . . still, I repeat, there can be but one fever. . . . Thus fire is an unit, whether it be produced by friction, percussion, electricity, fermentation, or by a piece of wood or coal in a state of inflammation.”[56]

“I have said that there is but one fever. Of course I do not admit of its artificial division into genera and species; a disease which so frequently changes its form and place, should never have been designated, like plants and animals, by unchangeable characters. . . . Much mischief has been done by nosological arrangements of diseases. They erect imaginary boundaries between things which are of an homogeneous nature. . . . They gratify indolence in a physician, by fixing his attention upon the name of a disease, and thereby leading him to neglect the varying state of the system, &c.”[57]

So much then having been said and written upon the disease in question, one might be apt to suppose that the nature of fever would have been thoroughly investigated, and its causes explained in the most satisfactory manner, long before this time. Instead of this, however, we find it still like a word which every body uses, and nobody understands. Dr. Fordyce, who has lately written a treatise on the subject, endeavours to prove that there is not any single symptom from the existence of which we can certainly determine the presence of this disease. “Fever (says he) has obtained its name in Greek, Latin, Arabic and Persian, principally from the idea of heat: pur, in Greek fire; febris in Latin, from fervere, to burn,” &c. This idea, he goes on to demonstrate, is erroneous; as the body of a feverish patient frequently sinks the thermometer below the natural standard; while the patient sometimes finds himself cold when the thermometer shows him to be really hot, and hot while the same instrument shows him to be cold. Neither is cold, followed by heat, a certain indication of the presence of fever, as many fevers begin without any previous sensation of cold. Frequency of the pulse also is no certain sign; and having discussed this last symptom he concludes thus. “If we examine the restlessness, anxiety, state of the tongue, head-ach, or any other of the symptoms which often take place in fever, we shall find that they also may be present when there is no fever, and absent in a patient afflicted with this disease; and therefore we cannot allow that there is any pathognomic symptom of fever.”[58] Dr. Rush declines giving any definition of fever;[59] but, with all due deference to these two very experienced physicians, we must account such extreme scepticism altogether erroneous. If fever cannot be defined, it cannot be described; for a definition is no other than a short description. If again there be no single symptom by which the presence of fever can be known, it is impossible that there can be any combination by which it can be known, any more than we can form an unit by any combination of cyphers. In fact Dr. Fordyce himself is at last obliged to acknowledge that there is a certain symptom with which fever generally begins; and, by his insisting upon it in various parts of the work, we must certainly be induced to suppose that it was by this sign principally that he determined whether his patients had a fever or not. “The first appearance (says he) which generally takes place is uneasiness and restlessness; a general uneasiness, the patient feeling himself ill, but incapable of fixing on any particular part of the body. This uneasiness affects the mind at the same time. Perhaps in this case it is the mind that is first affected. . . . Along with this uneasiness there is a restlessness, the patient wishing to change his place or posture frequently; the mind cannot likewise rest upon one object; it often wanders from one to another subject. At the same time there is a feel of weariness which resists the disposition in the patient to change his place and posture, and resists the disposition of the mind to alter the object of its attention, rendering the wish for such changes ineffectual. With these arises an actual inability of exerting the muscular powers, or performing any of the functions of the body; and also an actual inability of exercising the great faculties of the mind, the powers of perception, memory, arrangement of ideas, and of the judgment, in the same degree that they existed in health. The degree in which these take place is extremely different in the attacks of different fevers; but these appearances are very rarely absent, although indeed they may also happen in other diseases.”

Dr. Rush accounts the lassitude with which fever begins, one of the transient phenomena of it; and this with other phenomena he calls symptoms. Such as are more permanent and fixed, and which by other writers have been reckoned different species, he calls states; and of these he enumerates forty. Such as have any relation to the plague are as follow.

I. The MALIGNANT state, known by attacking frequently without a chilly fit, is attended with coma, a depressed, slow or intermitting pulse, and sometimes by a natural temperature or coldness of the skin. . . . This depressed state of fever more frequently when left to itself terminates in petechiæ, buboes, carbuncles, abscesses and mortifications, according as the serum, lymph, or red blood, is effused in the viscera or external parts of the body.

2. The SYNOCHA, or common inflammatory state; attacking suddenly with chills, succeeded by a quick, frequent and tense pulse, great heat, thirst, and pains in the bones, joints, breast or sides.

3. The BILIOUS state of fever; known by a full, quick and tense pulse, or by a quick, full and round pulse without tension, and by a discharge of green, dark coloured or black bile from the stomach and bowels. This state sometimes assumes the form of an hectic; the patient feels no pain in his head, has a tolerable appetite, and is even able to sit up and do business.

4. The TYPHUS state; known by a weak and frequent pulse, a disposition to sleep, a torpor of the alimentary canal, tremors of the hands, a dry tongue, and, in some instances, a diarrhœa. Sometimes it assumes symptoms of synocha on the eleventh, fourteenth, and even twentieth days. The common name of this state is the nervous fever.

5. Intermissions, or the INTERMITTING and REMITTING states, occur most distinctly and universally in those which partake of the bilious diathesis.

6. The SWEATING state occurs not only in the plague, but in the yellow fever, small pox, pleurisy, rheumatism, hectic and intermitting states.

7. The FAINTING state; occurring in the plague, yellow fever, small pox, and some states of pleurisy.

8. The BURNING state. This is attended not only with an intolerable sensation of heat in the bowels, but with a burning sensation excited in those who touch the patient’s skin. It occurs mostly in the remitting fevers of Asia.

9. The CHILLY state differs from a common chilly fit by continuing four or five days, and to such a degree that the patient frequently cannot bear his arms out of bed. The coldness is most obstinate in the hands and feet. A coolness only of the skin attends in some cases, which is frequently mistaken for an absence of fever.

10. The INTESTINAL state; including the cholera morbus, diarrhœa, and cholic.

11, 12, 13, 14, 15. The APOPLECTIC, PHRENETIC, PARALYTIC, LETHARGIC and VERTIGINOUS states.

16. The ERUPTIVE state; including the small pox, measles, and other exanthemata of Dr. Cullen.

17. The HÆMORRHAGIC state; known by fluxes of blood from various parts of the body.

18. The CONVULSIVE or SPASMODIC state. Convulsions are frequently attendant on the malignant state of fever.

19. The CUTANEOUS state; attended with various eruptions on the skin, particularly petechiæ.

These include the most remarkable varieties described by physicians as different species. From the subsequent account of the symptoms of the plague, it will appear that this single distemper monopolises, as it were, the symptoms, at least the most dangerous and terrible, belonging to them all. Those nosologists therefore who suppose the states of fever above described to be different species, instead of saying that the plague belongs to one kind of fever, ought to say that it is a complication of a great many different kinds. But here a question arises: Do all the varieties of fever just now described, or do all the other fevers described by different authors, include all the different modes by which the plague makes its attack? If so, then we know that the plague really partakes of the nature of fever, or may be accounted the highest degree of it. This is the opinion of Dr. Rush; for in his 4th vol. p. 153, he considers the different inflammatory states of fever, according to their strength, in the following order. 1. The plague. 2. The yellow fever. 3. The natural small pox. 4. The malignant sore throat, &c. To this I can have but one objection, and to me it appears insuperable; viz. that the plague frequently destroys without any symptom of fever; and, if so, we must certainly account it a distemper of another kind. To decide this matter, let us compare the symptoms of the most violent fever with what happens in times of violent pestilence. We can scarce imagine a fever more powerful than that which destroys in five minutes, and the following is the description of it from Dr. Fordyce. “When the first attack of fever has been fatal, it has been classed among sudden deaths, and all of these have been very erroneously called apoplexy, or syncopy (fainting.). . . . When the attack is fatal, it sometimes kills in five minutes, sometimes it requires half an hour, seldom longer than that time. While the patient is yet sensible, violent head-ach with a great sense of a chilliness takes place, the extremities become very cold, and perfectly insensible; there is great prostration of strength, so that the patient is incapable of supporting himself in an erect posture; he becomes pale, his skin is of a dirty brown, and he is soon insensible to external objects; the eyes are half-open, and the cornea somewhat contracted. If the patient goes off very soon, the pulse is diminished, and at last lost, without any frequency taking place, but if it be longer before he dies, the pulse becomes excessively small and frequent; all the appearances of life gradually subside, and the patient is carried off. Of this the author has seen instances, sometimes at the first attack, oftener in the returns of the disease, although very few.”

This no doubt is very terrible, and no plague whatever can exceed it. Indeed, when death is the termination, it signifies little what the disease is called. But the question is not whether fever or plague is the most dreadful, but whether they are the same. Now, from the above description, it is plain that fever never kills without some warning. In the present instance, head-ach and chilliness give a certain, though short, warning of the ensuing catastrophe; but, in violent plagues, Dr. Sydenham informs us, that people have been suddenly destroyed as if by lightning. Dr. Guthrie assures us that in the last plague at Moscow he has seen soldiers drop down suddenly as if they had been struck by lightning, or by a musket ball; yet some of these recovered by bleeding and proper management; but it is certainly not unreasonable to suppose that many, who were not thus taken care of, perished. Dr. Hodges speaks of the contagion of the plague in the most energetic terms. He says, “it is so rare, subtile, volatile and fine, that it insinuates into, and resides in, the very pores and interstices of the aerial particles. It is said to be of a poisonous nature also, from its similitude to the nature of a poison, so that they seem to differ in degree only; for the deadly quality of a pestilence vastly exceeds either the arsenical minerals, the most poisonous animals or insects, or the killing vegetables; nay, the pestilence seems to be a composition of all the other poisons together, as well as in its fatal efficacies to excel them. . . . The contagion of the plague is more active than lightning, and in the twinkling of an eye carries to a distance putrefaction, mortification and death. As for the manner whereby it kills, its approaches are generally so secret, that persons seized with it seem to be fallen into an ambuscade or a snare, of which there seems to be no suspicion. . . . In the plague of 1665, as in many others, people frequently died without any symptoms of horror, thirst, or concomitant fever. A woman, who was the only one left alive of a family, and in her own opinion in perfect health, perceived upon her breast the pestilential spots, which she looked upon to be the fatal tokens; and in a very short space died, without feeling any other disorder, or forerunner of death. . . . A youth of a good constitution, after he had found himself suddenly marked with the tokens, believed at first that they were not the genuine marks, because he found himself so well; yet he was dead in less than four hours, as his physician had prognosticated. A fever, however, did for the most part show itself, and was always of the worst kind. Sometimes it seemed to resemble a quoridian, sometimes a tertian; there never was a total cessation, but every exacerbation was worse than before.” In like manner the author of the Journal of the Plague Year informs us that many, supposing themselves, and supposed by others, to be in good health, would suddenly find themselves seized with great sickness, crawl to a bench, and instantly expire. “Many (says Dr. Hodges) in the middle of their employ, with their friends and other engagements, would suddenly fall into profound, and often deadly sleeps.”

It is needless to multiply examples: the above are sufficient to show that the plague, when in its most violent state, kills suddenly and imperceptibly, and that like the bite of a vampire,[60] without producing any sensible disorder. In a state somewhat inferior, it excites the most malignant fevers; in one still inferior it produces fevers of a milder nature, and so on until we find it so mild, that those infected with it are not even confined to their bed. In all this inquiry, however, we find the secrecy and invisibility of the pestilence, so often mentioned in scripture, still confirmed. Other distempers may “waste openly at noon-day,” but this always “walks in darkness.”

In one of the inferior stages of this distemper the body is affected with those eruptions named buboes and carbuncles. Dr. Patrick Russel, in his treatise on the plague at Aleppo, divides the symptoms of the distemper into six classes. In the first there were no eruptions, and all the patients of this class died. In the second, and all the rest, there were buboes and carbuncles. But, in the latter of these especially, it is worthy of remark, that they appear neither as a suppuration, nor as a common mortification, but like the eschar formed by a caustic, which can scarcely be cut by a knife. This appearance is not to be met with in any other disease. In many there are mortifications of various parts of the body, but all these are soft, and seemingly corruptions of the flesh. When a person dies of any ordinary distemper, the flesh soon corrupts and dissolves, but there is no example of its turning to a hard eschar like that made by a hot iron, or the caustic with which issues are made. This shews not merely a cessation of life, but the operation of some very active power in the body, like fire, tending to destroy the texture of it entirely, and to reduce it to a cinder. This power seems also to operate internally in the fleshy parts; for when the bodies of those were opened who died with the tokens, as they are called by Dr. Hodges, upon them, the mortification was always found much larger inwardly than it appeared to be on the outside. The tokens themselves are by Dr. Hodges called “minute distinct biasts, which had their origin from within, and rose up in little pyramidal protuberances, sometimes as small as pins’ heads, at others as large as a silver penny; having the pestilential poison chiefly collected at their bases,” &c.

That the plague was by the ancients reckoned a disease of a nature different from all others, appears from Galen, as quoted by Deusingius. “What is called the pestilence is most properly remarked by Galen not to be a genus of any known disease. For whatever diseases and symptoms are associated with the plague, truly and properly so called, the same are wont to be called pestilential diseases; of which indeed there are an innumerable multitude, and these not always nor every where the same.”[61]

In like manner Diemerbroeck, as quoted by Allen, gives his opinion, that “The plague is something different from a fever, and a fever is only a symptom of it, as I have very often observed; and therefore some very ill define the plague by a fever, since a fever does not essentially belong to it. . . . A pestilential fever, the companion of the plague, is not occasioned by a pestilential venom, but by the mediation of putrefaction; that is, it is not produced because the humours are infected with the pestilent venom, but because the heart, being irritated, overwhelmed and much weakened by the pestilent venom, can neither duly digest and rarefy, nor govern and sufficiently discharge the infected humours; which for this reason putrefy and acquire a preternatural heat, and so excite a fever; which by reason of the foresaid secondary cause, is different and distinct from the plague, and a symptom of it. This is confirmed both by the maxims and authority of the ancients and moderns, as well as by practice, and evident examples.”

Thus it appears, both by fair reasoning by induction from facts, and from the authority of the greatest physicians, that the plague is certainly a disease by itself, and entirely distinct from all others. Hence it follows, that, though we could investigate the causes of fever in their utmost extent, we might still be ignorant of the true plague. That nothing, however, may be omitted, let us now consider what physicians have advanced on this subject, and what progress they have made in ascertaining the sources from whence so many direful calamities are derived.

In an inquiry of this kind, or indeed concerning any cause whatever, it is plain that the nature of the effect must be first understood. Fever then being an effect, we must begin with investigating its nature. But fever itself is only manifest by certain changes in the human body. Before we can investigate the nature of fever, therefore, we must investigate the human body, and that in a manner very different from what we did before. We must now consider the sources of life; in what manner the vital principle acts upon the body, and by what means its motions can be disturbed, or how they may be rectified when once disordered, &c. &c.

The systems of medicine before the time of Boerhaave are now so generally exploded, that it is needless to take any notice of them; and the reputation of Boerhaave himself in this way seems to be almost expiring. His doctrines, nevertheless, merit some attention, because he takes into account a principle overlooked by succeeding theorists, viz. the cohesion of the parts of the body. That he did so is evident, from his having written upon the diseases of a weak and lax fibre, and the diseases of a strong and rigid fibre. In other respects he followed in a great measure the mechanical physicians of the former century. He therefore took but little notice of the nervous system, as being less subject, or indeed to appearance not at all subject, to the known laws of mechanics. The blood was more manageable. The microscopical discoveries of Lewenhoeck furnished an excellent foundation for his system. This celebrated observer had discovered, or fancied he had discovered, that the red part of the blood is composed of globules. Inaccurate indeed these globules must have been, since each of them was composed of six; four touching one another in the middle, with one above, and one below, thus

. The serum was said to be composed of single globules, and by this attenuation it was supposed that the fluid, instead of red, appeared of a yellow colour. Still, however, this was insufficient. Each of the yellow globules was discovered (either by fancied observations or by conjecture, it matters not which) to be composed of six others, which, singly taken, might constitute the lymph or some other fluid; and thus, like the number of the Beast, we might go on by sixes to the end of the chapter, and solve all the phenomena of nature. In justice to the microscopists, however, it must be observed, that some of them have given a much less fanciful account of the structure of the blood than Lewenhoeck. Mr. Hewson found it composed of vesicles, or small bladder-like substances, with a black spot in the middle. These vesicles dissolved in pure water, but kept their original form, which he says was as flat as a shilling, when a small portion of neutral salt was added to the fluid. The solid particles he supposed to be produced by the lymphatic system; the black particles by the spleen.

The supposed observations of Lewenhoeck were of considerable use to Boerhaave in the forming of his system of medicine, though they seem not to have accorded very well with his doctrine of lentor or viscidity in the blood. But, let this be as it will, having laid it down as the foundation of his theory, that the diseases of the body proceeded from too great a laxity of the fibres, or from too great a rigidity of them, and a great many from this lentor, his practice was accordingly directed to such medicines as he imagined would remove these supposed causes of disease. As the lentor of the blood was one of his favourite suppositions, he was therefore perpetually at war with this imaginary enemy, and dealt very much in saponaceous medicines with a view to break it down. But here it is evident that this great man was mistaken, even though we should allow the existence of lentor as much as he pleased. The viscidity, lentor, or any other state of the blood, is an effect of something. It is part of that state into which the body is brought by the disease. The efforts of the physician therefore ought to be against that which produces the lentor; for, unless this be done, the cause of the disease must perpetually counteract the medicines by producing new lentor as fast as they destroy it; and besides, must have greatly the advantage of the physician, by being already in possession of the whole mass of blood, while the medicines can only enter it very gradually, and that by the stomach and lacteals, instead of being instantly mixed with it, and exerting their power immediately upon the fluid itself.

But besides this mistake, which is common to other systems, Boerhaave’s lentor has been denied, and that upon such strong grounds that it is now universally exploded. Another system quickly succeeded, in which every thing was managed by the nerves. This was introduced by Hoffman, adopted, and perhaps improved, by Dr. Cullen, under whose auspices it acquired such a degree of celebrity, that for a long time it was dangerous to write or speak against it; and the person who had the audacity to do so underwent a kind of medical proscription from the Edinburgh College and all its students. According to this celebrated theorist, the brain is that part of the body first formed in the embryo; it may be seen with nerves proceeding; from it long before the heart or any blood-vessel belonging to it is visible. Hence we are to conclude that this part is necessary to the existence of every other part of the body, though it doth not appear that they are essentially necessary to its existence. The superiority of the nerves to all other parts being thus established, the Doctor undertook to prove that all other parts of the body were formed from them; that the body is nourished immediately from them, and in short that the whole body is in such subjection to the nervous system, that, except for the mere purpose of distending the vessels, we can scarcely know for what end the blood exists; since the nerves can alter its consistence, or that of any of the fluids secreted from it, by a mere affection of that system, without any thing either added to or taken from the vital fluid.

Thus we were compelled to believe that all diseases at their first origin are affections of the nervous system, from whence they are propagated through the whole body. The Cullenian practice in acute diseases, of which the plague is the most violent, was built upon a maxim of Hoffman: “Atonia gigoit spasmos:” Atony produces spasms. In explaining the nature of typhus fever, therefore, with which he classes the plague, the Doctor supposed that the contagion acted first upon the nervous system, by producing therein a debility. The immediate effect of this debility is a spasm, or preternatural contraction of the capillary vessels, or extremely small arteries. Hence the blood finds some difficulty in circulating, and the patient is seized with shivering, and has a sense of cold. When this has continued for some time the system begins to re-act against its enemy; the spasm is resolved, and, the reaction of the system continuing, the action of the heart and arteries is augmented, and the body becomes warmer.

Thus the coldness, shivering, and consequent heat, which constitute the first attack of fever, are very plausibly explained; but in the mode of cure this learned physician fell into the same mistake with Dr. Boerhaave; for though spasm is undoubtedly, even according to himself, an effect, he directs his medicines entirely against it, as if it were a cause. Thus, forgetting what he had just before advanced, that the spasm is occasioned by debility, he recommended the most debilitating medicines and regimen to cure people already too much debilitated; and to such practice his enemies alledged that many fell victims. The theory and practice, however, still kept its ground; and as great numbers of students were every year bred up in the belief of it at Edinburgh College, who carried the principles of their teacher to all parts of the world, it bade fair for becoming universal. But, in the midst of this eclat, the whole system received such a rude shock from the doctrines of John Brown, though at that time not even M. D. as it hath not yet recovered.

Though the author of the new system contended, as much as Dr. Cullen, for the supremacy of the nerves, he did not upon that foundation attempt to establish his practice. He considered the living body as one machine, the whole of which might be acted upon, and always was acted upon by certain powers. It possesses a certain inexplicable property called excitability, capable of being augmented or diminished. Every power which augments the excitability he called a stimulus; the opposite would have been a sedative; but according to this system there is not any sedative, nor can there be one in nature. The reason is, that excitability itself has no existence but in consequence of the action of certain powers called stimulants. The total subduction of these reduces the excitability to nothing; of consequence no power can act against it in a state of non-existence. What other physicians call sedatives, therefore, according to the new system, are only weak stimulants. The fallacy of such reasoning is obvious; but as it does not affect the practice, we shall not spend any time in considering it further.

On the principles just now laid down, the Brunonian system divides all diseases to which the human body is liable into two great classes; the one produced by too much excitement, the other by too little. The former contains those diseases by other physicians called inflammatory; the latter such as are called nervous, putrid, or all in which the powers of life are too weak, and require to be supported. This last is supposed to be much more numerous than the former; and in the cure of these it was that the founder of the system appeared to greatest advantage. A most violent altercation took place between Dr. Brown and the Edinburgh College; yet, notwithstanding all the influence of the professors, and their unanimous opposition to the new doctrines, they found themselves ultimately unable to resist a single man unsupported either by wealth or reputation. The plausibility of his system, and its being obvious to every capacity, overcame every obstacle; so that even the practice of the Cullenians themselves underwent considerable alterations. It is not, however, to be denied that the system hath been considerably improved, or at least altered, by some of Dr. Brown’s pupils, who have had the advantage of extensive practice, and of visiting many different countries; which the Doctor himself never had. His materia medica was besides exceedingly confined; the only medicines he had any great opinion of, being laudanum and ardent spirits. The Peruvian bark he held in very little estimation, as being a weak stimulus. He seems to have been unacquainted with the virtues of mercury, except in the venereal disease, and most probably would have given laudanum in those cases of fever where mercury is found by others to be so efficacious. But this deficiency hath been abundantly supplied by some of his followers. In a work entitled “The Science of Life,” published by Dr. Yates and Mr. McLean, practitioners in the East Indies, we find mercury exhibited in prodigious doses. As a specimen we shall select their third case, which was a dysentery. On the first of September the patient took two grains of calomel and as much opium every two hours. This was continued for two days. On the third, the dose was given every hour; besides which, he had half an ounce of mercurial ointment with a drachm of calomel rubbed into his body. Next day the pills were continued, and the quantity of ointment tripled by thrice rubbing in. This was continued for three days, at which time, an eruption on the skin appearing, it was feared he could not be salivated; this eruption being a sign that no salivation could be produced. The same mode of treatment, however, was persisted in. September 7th the calomel in the pills was augmented to four grains; the warm bath was used, and the ointment continued; but at night twenty grains of calomel and six of opium were given every two hours. At the same time two ounces of ointment, with four of calomel, were ordered to be rubbed in. Next day, though his pulse was almost imperceptible, and his extremities cold, “the medicines were continued as far as circumstances would admit;” with what view it is not said, nor indeed is it easy to be discovered. At one in the morning, however, the patient died; an event not at all surprising. Our authors excuse themselves for this failure by saying that the viscera of the patient were diseased, as was evinced by the impossibility of exciting a salivation; and “that when a patient is evidently incurable by the common practice, it becomes the duty of the practitioner to depart from it.”

No doubt we may readily assent to both these assertions; but though a patient be evidently incurable by the common practice, or by any other, there is no necessity for killing him, or for persevering in a course of violent medicines that evidently make him worse. The whole of this case indeed strongly militates against the doctrine of excitement; for if mercury be such a powerful stimulus to the powers of life in general, how comes it to pass that in the present case the unhappy patient, instead of being in the smallest degree excited, was prodigiously debilitated, and that from the very first time of taking the medicines. This will appear from the following table, exhibiting the symptoms of the disease as they kept pace with the medicines taken.

From a consideration of this patient’s symptoms, in comparison with the quantity of mercury taken, it most evidently appears, that it acted in no other way than as an irritating poison; affecting, with extreme violence, the already diseased intestines, and, instead of exciting the vital powers of the whole system, manifestly destroying them. Let it not be imagined, however, that this case is selected from the rest merely because it was fatal, or because it affords an opportunity of finding fault with the practice recommended in the book. It is the only one in which the mercury had a fair trial; and even here it was not very fair, as being conjoined with a great quantity of opium. In the other cases, which terminated favourably, the mercury was overpowered by such horrible doses of opium, that we cannot tell which medicine had the greatest share in the cure; besides, that in other cases the patients were allowed the free use of wine, which we all know to be a powerful stimulant and cordial; but it is not said that the poor man, whose case is above related, had a single drop of wine, or any thing else, except opium, to support him against the action of such a violent medicine.

On this case it is of importance still to remark, that it affords, in the strongest manner, an argument against what our authors say, p. 86, that “mercury acts by supporting the excitement of the whole body, it invigorates each particular part; and thus occasions, to a certain extent, the regeneration of those organs which may have been injured by disease.” In the instance adduced, there is no evidence of a stimulus upon any other part of the system than the bowels, which were already debilitated or diseased in such a manner that they could not bear it. The system in general, instead of being excited, was sunk and debilitated from the very first moment, until at last the excitement terminated entirely by the patient’s death. But further: There is very little probability that mercury or any other medicine whatever can prove a general stimulus, and that for the following reasons.

1. No medicine can assimilate with the substance of the body. Medicines properly so called are here alluded to. Food or drink of any kind taken for the support of the body while in health, however they may act medicinally upon occasions, are excepted.

2. The body is composed of many various substances, each differing in its nature from the other. The nature of the medicine, whatever it may be, is uniform, and cannot act upon substances of different kinds in an uniform manner; and without this there can neither be an universal stimulant, nor an universal debilitant.

3. All medicines, being incapable of assimilation with the body, must be considered, when taken into it, as foreign matter; and the introduction of them at any rate is in fact the creating of a disease. This is evident from multitudes of instances where people by quacking with themselves, and taking medicines unnecessarily, have destroyed their health.

4. As every medicine has one peculiar nature, and one mode of action in consequence of that nature, it must, when introduced into the body, where there are fluids of various natures, act upon one of them more than the rest; and this may be called the chemical action of that medicine upon the body.

5. In consequence of the chemical action of the medicine, the mode by which it is expelled out of the body will be different; for, as all medicines are extraneous substances, they must be sent out of the body as fast as possible; and it is their action upon one particular part which promotes their expulsion. Thus, if from the nature of the medicine it acts in a certain way upon the stomach and bowels, it will vomit or purge, or perhaps both; and by this action it is expelled from the body, along with whatever other matters happen to be in the stomach or intestines; and thus medicines do good only accidentally; for mere vomiting or purging are most certainly diseases; but where noxious matters exist in the bowels, and do not naturally excite these operations, an emetic or purgative is unquestionably useful. Here the authors of the Science of Life reason differently; and it is worth while to refute their argument, as being the foundation of such tremendous practice as nobody of common sense would choose to be the subject of. Of tartar emetic they speak in the following terms. “That tartar emetic is a stimulant of very high power, is evident from the small quantity of it which produces the state of indirect debility that occasions vomiting. It should be given in such a manner as to increase and to support the excitement. But this will be found difficult, as the duration of its action seems to be even shorter than that of opium. If its action does not continue more than a quarter of an hour, might it not be repeated at such short intervals, and the doses so reduced as to allow the establishment of the indirect debility?” This is arguing in a circle. They first suppose that vomiting is occasioned by indirect debility, that is, the weakness produced by an excessive stimulus to the whole system, as in cases of drunkenness; and then, from the existence of vomiting, they prove that a general stimulus had pre-existed. The cases, however, are widely different. In cases of drunkenness, the person feels himself at first exhilarated, alert and active, which shows the existence of a general stimulus. But who has ever found himself exhilarated by taking a dose of tartar emetic? Yet in a general excitement it is absolutely necessary that this exhilaration should take place, because it is an inseparable consequence of an addition of vital power, let it come in what way it will. Thus we know that if a person happens to be much exhausted by fatigue and abstinence, he will be exhilarated and his strength augmented by a single mouthful of meat, as well as by a glass of wine. This shows that both these are general stimulants to the system; but what medicine have we that will produce similar effects? Perhaps opium comes the nearest in the whole materia medica; but the uneasiness it occasions in the stomach manifests a greater action upon it than the other parts; for if the whole body were equally excited, the withdrawing of the stimulus, or its naturally losing its force, could only have the same effect with fasting or fatigue; but the debility of the stomach, the confusion of the head, and other effects which attend a dose of opium, demonstrate that it acts partially, and not equally over the whole body. The Science of Life indeed says that these effects are owing to the improper omission of the medicine, or not repeating the doses in due time. This may be; but no improper exhibition of food, or want of due repetition, will produce such symptoms; which undoubtedly is a proof that food stimulates the system in one way, and opium in another.

6. If any medicine could be found that acted as an universal stimulus or exciter of the whole system, it could not like others be expelled, by any particular evacuation; but, by destroying the balance between the force of the acting powers and the subject on which they act, would most certainly kill, unless very powerful means were used to counteract its effect. The only stimulant we are acquainted with which acts equally on the whole system, and which can be readily exhibited as a medicine, is that pure kind of air called by Dr. Priestley dephlogisticated, by Scheele empyrean, and by the French chemists and their followers oxygen. The exciting powers of this air, when breathed instead of the ordinary atmosphere, are astonishing. It not only augments the appetite, but the power of the muscles, and the inclination to use them; so that without any intoxication or delirium the person cannot refrain from action; and it not only exhilarates the spirits in an extraordinary manner, but beautifies the face. Did the cure of diseases therefore, or any set of them, depend on mere excitation, no other medicine but oxygen would be necessary. What effects it may have in diseases of debility is not yet ascertained; but to persons in health it certainly proves fatal: their bodies are unable to bear its powerful action, and of consequence they waste, and would die of consumptions, if its effects were not counteracted. Nor is this at all an easy matter; for Dr. Beddoes informs us that, by breathing this air for a short time each day, only for three weeks, he found himself in great danger of a consumption, and was obliged to use much butter and fat meat in his diet, besides giving up the use of the air altogether, in order to get clear of its mischievous effects.

Another mode of stimulating or exciting the whole system is, by putting into it a larger quantity of blood than it naturally contains. This is entirely similar to the breathing of oxygen; especially if arterial blood be used, which has already imbibed its spiritous part from the atmosphere. In the last century the transfusion of blood was proposed not only as a mode of curing diseases, but of restoring old people to youth; and Dr. McKenzie, in his Treatise on Health, quotes from the memoirs of the Academy of Sciences several instances of the blood of brute animals being infused into human veins, without any inconvenience. It seems, however, not only a bold but an unnatural attempt to use the blood of beasts for such a purpose; and, however lavish mankind may be of their blood upon certain occasions, it is to be feared that there are few who would be willing to spare any to relieve another from sickness; but indeed little can be said about the practice; as, on account of some bad consequences, or failures, it was forbidden by the king of France, and by the pope’s mandate in Italy, and has now fallen into disuse. In a paragraph at the end of Heister’s surgery (4to edition) it is asserted that the transfusion of blood was productive of madness. Dr. Darwin, however, in his Zoonomia, still proposes the transfusion of blood as a remedy, and even describes a convenient apparatus for performing the operation. In one part of his work he says, “Might not the transfusion of blood, suppose of four ounces daily, from a strong man, or other healthful animal, as a sheep or an ass, be used in the early state of nervous or putrid fevers?” In another place he mentions his having proposed it to a gentleman whose throat was entirely closed up by an incurable swelling, so that he could swallow nothing. This is a disease not very rare, and which always must be fatal; because the patients, though not affected by any sickness, die of hunger; and, to relieve them from this miserable situation, extraordinary attempts are not only allowable but laudable. The Doctor proposed to his patient, “to supply him daily with a few ounces of blood taken from an ass, or from the human animal, who is still more patient and tractable, in the following manner: To fix a silver pipe, about an inch long, to each extremity of a chicken’s gut, the part between the two silver ends to be measured by filling it with warm water; to put one end into the person hired for that purpose, so as to receive the blood returning from the extremity; and when the gut was quite full, and the blood running through the other silver end, to introduce that end into the vein of the patient, upwards towards the heart, so as to admit no air along with the blood. And, lastly, to support the gut and silver ends on a water plate filled with water of 98 degrees of heat; and, to measure how many ounces of blood were taken away, to compress the gut from the receiving pipe to the delivering pipe.” The gentleman desired a day to consider of this proposal, and then another; after which he totally refused it, saying that he was now too old to have much enjoyment of life, and that, being so far advanced in a journey which he must certainly accomplish sooner or later, he thought it better to proceed than return. The Doctor informs us that he died a few days afterwards, seemingly very easy, and careless about the matter. One experiment of this kind I have been witness to; not indeed on a human creature, but on a calf. This creature received into one of its jugular veins a considerable quantity of blood from the carotid artery of another, nearly of the same age (about a month, or little more.) It was impossible to say any thing about how much was transfused; only the bleeding was continued till the animal which lost the blood began to shew signs of faintness. The artery was then tied up, and the orifice in the jugular vein closed. The calf which had lost the blood appeared very languid and faint, but lived a few days in a drooping state; when it either died of itself, or was killed, as being supposed past recovery. The other, which had received the blood, appeared to be in every respect highly excited. It became playful, even in the room where the operation was performed, its eyes assumed a bright and shining appearance, and its appetite was greatly increased. Thus it continued for about a fortnight; appearing all the time to be in high health, and eating much more than usual; but at last died suddenly in the night. From these effects on healthy subjects, however, we cannot infer what would happen in such as are diseased; but it is plain that if the cure of diseases were to depend upon mere excitation, the means are in our power, without any local irritation, which always must take place in some degree by the use of ordinary medicines. This path is not absolutely untrodden: the pneumatic practitioners of the present day have tried oxygen in consumptions, and found it pernicious; and Dr. McKenzie informs us that the transfusion of blood was tried ineffectually in the same.

7. As all the medicines usually prescribed at present are only to be accounted partially stimulant, or as acting upon particular parts of the system, we see that some may promote one evacuation, and some another; while all produce some change in the organization, which may prove useful or detrimental, may increase the disease or cure it, or may produce another, according to the judicious or injudicious application. But for a knowledge of all this we must be indebted to experience: there is not a theory on earth that can lead us a single step.

Before we dismiss the consideration of medical theories, however, it will still be necessary to give some account of the new system as it hath branched out in various ways: for though the fundamental principle is now received by a great number of physicians, yet the superstructure is exceedingly different from what Dr. Brown himself erected and, indeed, from the very same principles we find conclusions made as directly opposite to one another as can be expressed in words. Drs. Yates and McLean, for instance, at Calcutta in the East Indies, have concluded that the plague “is a disease of a very high degree of exhaustion;” which Dr. Brown would have called debility. Dr. Rush at Philadelphia, proceeding also upon the Brunonian principles, determines it to be the most inflammatory of all diseases,[62] and which Dr. Brown would have called a disease of excitement. These two doctrines are, in every sense of the word, as distant from one another as east from west. Let us then consider both, if any consideration can avail us on the subject.

By the ancients it was supposed that diseases were occasioned by something either bred in the body or received into it, and that the power of nature produced, during the course of the disease, a certain change in this matter, called coction, or concoction; which, if we please, we may express by the English word cooking. The matter of the disease, called also morbific matter, thus cooked, was in a state proper for expulsion, and was therefore thrown out by sweat, vomit, stool, &c. or it might be expelled artificially, which could not have been attempted with safety before. Modern systems deny the existence of morbific matter, and resolve all into an affection of the nerves, according to Dr. Cullen by certain sedative causes, but according to Dr. Brown by an accumulation in some cases, and an exhaustion in others, of the excitability or excitement of the body. The Science of Life commences with stating what they suppose to be an improvement of the Brunonian principles, and from which the following account of the origin of diseases is extracted. “Upon the different states of excitability depend all the phenomena of health and disease. There are three states of the excitability. 1. The state of accumulation; when a portion of the usual stimuli is withheld. . . . When a portion of the usual stimuli is withheld, the excitability accumulates, and the body becomes susceptible of impression in the direct ratio of the subduction. This state constitutes diseases of accumulation, or of direct debility. 2. The middle state; when the excitability is such that the application of the accustomed degree of exciting powers produces tone or health. 3. The state of exhaustion. When the application of stimuli has been greater than that which produces healthy action, the excitability is exhausted, and the body becomes less susceptible of impression in the direct ratio of the excess. This state constitutes diseases of exhaustion, or of indirect debility. The states of accumulation and exhaustion of the excitability, in their different degrees, constitute all the diseases to which living bodies are subject.”

Here the chime runs on the word excitability, which is not defined. If we call this property life, then we are only informed, that, as life is more or less vigorous, the body enjoys a greater or smaller degree of health; which we know without any medical instructor. If, instead of the accumulation and exhaustion of excitability, we take the original doctrine of excitement and debility laid down by Dr. Brown himself, we are nothing better. The whole theory is lost for want of the definition of a single word. As long as excitability remains an unknown property, we can explain nothing by it. We may indeed vary our terms. We may call it nervous influence with Dr. Cullen, or sensorial power with Dr. Darwin; but we shall still be as much in the dark as ever; and all that can be made out of our theories, when our language is decyphered, must be, that sometimes people are well, and sometimes they are sick!

Dr. Rush, in his Treatise on the Proximate Cause of Fever, adopts in part Dr. Brown’s system pretty nearly as the author himself laid it down. “Fevers of all kinds (says he) are preceded by general debility. This debility is of two kinds, viz. direct and indirect. The former depends upon an abstraction of usual and natural stimuli; the latter upon an increase of natural, or upon the action of preternatural, stimuli upon the body. . . . Debility is always succeeded by increased excitability, or a greater aptitude to be acted upon by stimuli. . . . The diminution or abstraction of one stimulus is always followed by the increased action of others.” Here it is evident we are as much in want of definitions as ever. We know neither what excitability is, nor what debility is, and yet they are both held out as the causes, and proximate or immediate causes, too, of symptoms produced by things quite obvious to our senses. Thus cold and heat, with which we are daily conversant, are only called the predisposing causes of fever; while debility and excitement, words to which we have no meaning, are said to be the proximate cause. It would certainly be better to throw away such words altogether, and say that cold, heat, &c. cause fevers, without troubling ourselves farther about the matter.

It remains now to take into consideration the pneumatic theories, founded upon the discoveries made by Dr. Black, Dr. Priestley, Lavoisier, and others, concerning various kinds of aerial fluids, or gases,[63] as they are also called. Some of these, particularly that afterwards called fixed air, were discovered by Van Helmont. Considerable advances were made by a German chemist, named Mayow, in the last century; but his book had fallen into such oblivion that his name was scarce ever mentioned, until his discoveries were repeated, and still greater advances made by others. Dr. Hales obtained air from a great many different substances, but was unable to ascertain any thing concerning its nature. Dr. Black of Edinburgh laid the foundation of pneumatic chemistry, by discovering that a certain species of air is capable of being absorbed by earths of different kinds, and that many very heavy substances owe at least one half of their weight to this condensed air. The discovery was accidental. Wishing to obtain a very pure and white lime, he had recourse to the fine white earth called magnesia alba. Some of this he distilled with a heat sufficient to make the vessel red hot. Only a very small quantity of water came over, but the magnesia had lost almost two thirds of its weight. This immense loss was found to arise from an emission of air during the operation; and by other experiments it was likewise found that the air might be transferred from one portion of magnesia to another from which it had been previously expelled; that the existence of this species of air in certain bodies was the cause of that fermentation which takes place when any acid is poured upon them, as vinegar upon chalk or potash. Hence if any of these substances be deprived of its air, it will not any longer ferment in this manner. It must not be forgot, however, that when air thus unites itself with any terrestrial substance it no longer has its former properties. It is reduced exceedingly in bulk, and in proportion to this reduction only the body is increased in weight; and therefore though we say that the air is absorbed, we must still remember that only one part of it is so, and that by far the least considerable in bulk. A violent fire will always expel the air again, and restore it to its former bulk; and again the condensation or absorption of the air is always attended with the production of heat. This last property was not much attended to by Dr. Black, but others have observed it; and the late Dr. Charles Webster of Edinburgh published a theory in which he maintained that condensation was in all cases the cause of of heat. But, however true it may be that condensation of any kind is followed or accompanied by heat, it is evidently necessary to know the cause of the condensation also, otherwise we make no advance in solid theory.

The aerial fluid, discovered by Dr. Black, was one of those most commonly met with. He called it fixed air, from its property of adhering or fixing itself to different bodies. It was found to be the same with that which had been discovered by Van Helmont, and by him named gas sylvestre (spirit of wood)[64] or the fume of charcoal; it was found to be the same with the steam of fermenting liquor, and with that very frequent and dangerous vapour, met with in coal mines, called in Scotland the choke-damp. Like other discoveries, this was quickly pushed beyond its proper bounds, and applied to the solution of phenomena which it could not solve. Dr. MBride, particularly, supposed it to be the bond of union between the particles of matter, or in other words the principle of cohesion itself. It was also supposed to be the substance of those scorching winds, called samiel, met with in Asia and Africa, and which sometimes prove fatal to travellers. The pernicious vapours called mofetes, which sometimes issue from the old lavas of Vesuvius in Italy, were likewise supposed to be the same;[65] but of this, particularly with regard to the samiel, there seems to be no sufficient evidence.

The industry of other experimenters did not long leave theorists without abundance of materials upon which they might exercise their talents. It is impossible in this place to assign to each his proper rank in the way of discovery, or indeed to mention their names. Dr. Priestley has distinguished himself far above the rest. He not only repeated and improved Dr. Black’s experiments on fixed air, but likewise found out a number of other kinds; particularly that from animal substances in a state of putrefaction, which is so pernicious to living creatures, insects excepted; for these last will thrive amazingly in air that would prove certain death to a man. He also discovered that this kind of air, and some others, were absorbed by vegetables, and thence inferred the use of vegetables in purifying the atmosphere. He even analysed the atmosphere itself, and found that it consisted of two different kinds of fluids, one of which he called dephlogisticated, the other phlogisticated air. The former was found to support animal life for a time, the latter to destroy it instantly. Their effects upon fire were the same; the former exciting the most vehement heat and bright flame, the latter extinguishing a fire at once.

The fame of Dr. Priestley’s discoveries quickly reached the continent of Europe; the French chemists repeated his experiments with improvements, as they thought; and indeed certainly made many curious discoveries. Lavoisier was particularly remarkable for his numerous and accurate experiments; but, by his changing entirely the language of former chemists, and substituting a set of new terms of his own invention, he certainly entailed the greatest curse upon the science it ever met with. It belongs not to this treatise to give an account of his system farther than to say, that, from the immense proportion of condensed aerial matter found in most terrestrial substances, he and his followers were led to conclude, that different species of air constitute almost the whole of the terraqueous globe. Water particularly they have absolutely and most positively determined to be a composition of two airs condensed, viz. the dephlogisticated and inflammable, which they call oxygen and hydrogen. However, this doctrine is still opposed by Dr. Priestley and some others.

In the midst of so much theory, and so many new and surprising discoveries, it would have been wonderful indeed if the science of medicine had kept free from innovation. It did not: the new chemistry, with all its formidable apparatus of hard words, was introduced, and thus the study of the science, already very difficult, was rendered still more so. In passing this censure upon the modern nomenclature, as it is called, I am sensible that I must rank with the minority; nevertheless, I have the satisfaction of finding that I am not altogether singular. Dr. Ferriar, in the preface to his second volume, complains, “that, with every attempt towards the formation of a system, new applications of words are introduced, which, though desirable in the art of poetry, are very inconvenient in pathological books, especially when this is done to give an air of novelty to old theories and observations. For, between the ancient language, which practitioners cannot entirely reject, and the new dialect, which they cannot wholly adopt, the style of medical books is reduced to a kind of jargon, that the author himself may possibly understand, but which his readers find it very difficult to unriddle. Hence results a neglect of medical literature, and hence the pernicious habit of regarding as new whatever has not appeared in the publications of the last half century.” To the same or a similar purpose, in the preface to his first volume, he cites Quintilian.[66] “Some have such a multitude of vain words, that, while they are afraid of speaking like other people, by a kind of affected elegance, they confound every thing they have to say with their immense loquacity.”

The pneumatic system naturally arose from a consideration of the composition of the atmosphere we breathe. Finding this fluid to be composed of two others, the one of which would preserve life for some time at least, and the other instantly destroy it, it became natural to think that diseases might be produced by any considerable variation in the proportion of these ingredients. An instrument was soon invented by which any considerable variation in this respect might be discovered; but upon trial this was found to be of very little use. Dr. Priestley himself tried, by means of this instrument, some very offensive air which had been brought from a manufactory, and could find no remarkable difference between it and that which was accounted pure. Still, however, it was evident that by increasing very much the proportion of one of the ingredients, some considerable alteration might be produced, which could not but be perceptible in the human body; and this led to the application of aerial chemistry to disorders of the lungs. The mixture chosen for this purpose was pure dephlogisticated (oxygen) with inflammable air (hydrogen;) and, though this has not been known to effect a radical cure, it certainly has given relief in many cases. In fevers also the application of fixed air (carbonic acid) hath been found advantageous; but with regard to oxygen and some others we have not yet a decided instance of their good effects in any case. Dr. Beddoes indeed is of opinion that it would be of service in the sea-scurvy; but in this (whether his conjecture be right or wrong) the theory is certainly erroneous, as shall presently be evinced.

In considering the pneumatic system it is evident that modern chemists have fallen into the same error with their predecessors, viz. of supposing that every thing which by the force of fire or otherwise they could produce, from any substance, previously existed in it. Hence, as from a piece of bone for instance, a chemist can produce water, salt, oil and earth, it was supposed that these four were the principles or elements of the bone. But this was false reasoning; for if these were really the chemical principles, they ought to have been able to produce some kind of bony substance by mixing them together after they had been distilled. But no such thing could be done; and though we should add to the mixture the whole quantity of air emitted during the distillation, and which escaped the notice of ancient chemists, our success would be no better. In like manner, because in certain circumstances oxygen is obtained from the flesh of animals, it has been concluded that it necessarily exists as an ingredient in their bodies while living; and that, if this kind of air happens to predominate, the animal will be affected in one way, or if hydrogen prevail, in another. But though we have already quoted Dr. Girtanner with approbation as having obtained oxygen gas from fresh meat, yet this does not by any means prove to us that it exists in flesh as one of its component parts. Even in the Doctor’s experiment it was necessary to expose the flesh to the atmosphere in order to procure the gas by distillation; which undoubtedly must excite a strong suspicion that the air in question comes from the atmosphere itself; and, if this is the case, it is not reasonable to suppose that a disease could be cured by any addition of oxygen to the solid parts; because, though sound flesh may have an inclination to absorb this kind of air, we do not know whether it would have such a property of absorption in a diseased state. Indeed in the scurvy, which Dr. Beddoes chooses as an example, experiment seems to determine in favour of fixed air rather than any other. But let us hear Dr. Girtanner himself, who has at large discussed this subject in two memoirs; one upon the laws of irritability, and another on the principle of irritatibility.

In these memoirs we find the Brunonian doctrine set forth with such silence in regard to Dr. Brown himself, that some have not scrupled to charge Dr. Girtanner with literary theft; but this is a matter which belongs not to us to consider: the theory may be very good, whether stolen or not. He changes the word excitability, used by Dr. Brown, for irritability; but hath the misfortune of not being able to tell us what he means by it. He goes on, however, to distinguish the three states of tone or health, accumulation, and exhaustion, as other Brunonians do. Health, he says, in a fibre “consists in a certain quantity of the irritable principle necessary for its preservation. To maintain this state, the action of the stimulus must be strong enough to carry off from the fibre the surplus of this irritable principle which the lungs and the circulation of the fluids are continually supplying. For this a certain equilibrium is necessary between the stimuli applied and the irritability of the fibre, in fine that the sum of all the stimuli acting upon it may be always nearly equal; powerful enough to carry off from the fibre the excess of its irritability, and not so strong as to carry off more than this excess. . . . When the sum of the stimuli acting upon the fibre is not great enough to carry off all its excess of irritability, the irritable principle accumulates in the fibre, and then it is found in that state which I call the state of accumulation; the irritable principle accumulates in the fibre, its irritability is augmented, and the stimuli produce much stronger contractions than when the fibre only retains its tone. . . . When the sum of the stimuli acting upon the fibre is too great, the fibre is deprived not only of the excess of its irritability, but also of some portion of the irritable principle necessary for the tone of the fibre; or, more properly speaking, the fibre loses more irritability than it receives, and, of course, in a short time finds itself in a state of exhaustion; and this exhaustion will be either temporary, or irreparable.”

Here it is evident that we have nothing but Dr. Brown’s system, without the least explanation to render it more intelligible. A definition is still wanting. This invisible and incomprehensible property of irritability ruins our whole fabric; nor can the deficiency be supplied by human art or skill: of consequence we must abandon this part of the system entirely, and come to something more cognizable by our senses. It is impossible, however, to pass over in silence the amazing inattention of the author, in imagining that on such unintelligible principles he could explain other phenomena. “In the state of temporary exhaustion (says he) the fibre loses its tone, and fails for want of irritability. The application of a stimulus while it is in this state will not make it contract. Provided the stimulus be not very strong, it will produce no effect at all, but in a short time the irritable principle will accumulate afresh in the fibre, and then it will again contract. It is only by little and little that the fibre recovers its irritability. This truth, I dare venture to say, is as new as it is striking. It unfolds a vast number of phenomena hitherto inexplicable.” Here we have nothing but the pompous declaration of a fact already well known; viz. that not only a fibre, but the whole body, may be in a state of temporary insensibility, and yet recover either of itself or by the use of external means. How many people have fallen into a syncope, and yet recovered! How many limbs have become paralytic, and in time recovered their sense and motion! Yet this is all that we are informed of with so much parade and assumption of novelty. We know that when a person is in a faint he is insensible to ordinary stimuli, though very strong ones will rouse him; but what can we infer from this? Nothing; only we see it is so. Does it avail us any thing to be told that during the time of fainting the irritability is exhausted, and “in a short time the irritable principle will accumulate afresh;” in which case the patient will no doubt recover, unless he happens to be dead, which is the true meaning of an irreparable exhaustion of the irritability.

In speaking of the principle of irritability he expresses himself in the following manner. “I think that the oxygen is absorbed by the blood, and that the venous blood is oxygenated in the lungs during respiration. The most celebrated naturalists and chemists are of a different opinion: they think that the oxygen does not combine with the venous blood. According to them, this last loses carbon and hydrogen, and recovers the bright colour natural to it, without absorbing any thing from the atmosphere. . . . After having a long time attended the phenomena of respiration, and made many experiments upon this subject, I think it may be concluded that one part of the oxygen of the vital air combines with the venous blood, of which it changes the black colour, and makes it vermilion;[67] the second part of the oxygen unites with the carbon contained in the carbonic-hydrogen gas, which exhales from the venous blood, and forms carbonic acid air; a third part unites with the carbon of the mucus, contained in great quantities in the lungs, and which is continually decomposing; this part also forms carbonic acid air; a fourth part of the oxygen combines with the hydrogen of the blood to form water.”

On this theory I shall only observe, that though I lay claim to the former part, I allow the Doctor all the latter part to himself; particularly where he speaks of the formation of water to be exhaled during respiration. The air in question consists of two parts, like fixed air already mentioned. One of these is capable of being attracted, condensed, or united with certain substances; the other vanishes, leaving no other traces of its having ever existed, but heat, greater or less according to circumstances. When the air is taken into the blood, one part of it undoubtedly combines with something thrown out by the lungs, and forms fixed air, of which our breath contains a considerable quantity. We know certainly that the condensable part of fixed air is formed out of the condensable part of the oxygen, with certain additions. As therefore great part of this condensable oxygen is thrown out in fixed air at every expiration, it is natural to suppose that all of it is so: at least we cannot know the contrary without a series of very difficult and tedious experiments, which have never been made by Dr. Girtanner or any body else. But if the whole of this condensable part be thrown out, none can enter the blood by the breath; and consequently whatever true oxygen may afterwards be expelled from that fluid, must be a factitious substance, formed either during the artificial process, used for distilling it, or by a natural process In the body itself. It is not therefore at all probable that the oxygen which flesh emits in distillation can be derived from the air by respiration.

Another and more probable source is the food and drink we take; all of which are more or less impregnated with air of different kinds, particularly fixed air. This, we know, very readily condenses, and certainly will do so when taken into the body. In this state it not only may, but certainly will, pass into the blood, and through all the different parts of the body, until, having accomplished its purpose, whatever that may be, it is thrown out by insensible perspiration, as has been already explained.

The conclusions drawn by Dr. Girtanner from his experiments are, 1. That the change of colour which the blood undergoes during the circulation is not owing to its combination with hydrogen air[68]. 2. The deep colour of the blood in the veins is owing to the carbon it contains. 3. That the vermilion colour of the arterial blood proceeds from the oxygen with which the blood is conjoined during its passage through the lungs. 4. That respiration is a process exactly analogous to the combustion and oxydation of metals; that these phenomena are the same, and to be explained in the same manner. 5. That, during circulation, the blood loses its oxygen, and charges itself with carbonic hydrogen air, by means of a double affinity. 6. That, during the distribution of the oxygen through the system, the heat which was united with this oxygen escapes; hence the animal heat. 7. That the great capacity of arterial blood for heat is owing to the oxygen with which it is united in the lungs.

On these propositions, which constitute in a great measure the fundamental principles of the doctrine of oxygenation of the human body, we may remark,

1. Nobody can reasonably suppose that hydrogen air is the cause of the dark colour of the blood in the veins, because there is no source from which it can be derived; and, besides, it is certain that no kind of air can exist in its elastic state in the blood, without destroying the life of the animal. Some experiments proving this are given by Dr. Girtanner himself. It is true that an aerial vapour, of the nature of fixed air, exhales from the body by insensible perspiration; but there can be no doubt that this receives its elasticity only at the surface of the body, and is expelled the moment it is formed. It has indeed been proved, by undeniable experiment, that no air of any kind exists in the larger veins; because a portion of a vein, included between two ligatures, being cut out, and put under the receiver of an air-pump, does not swell in the least when the air is exhausted, which yet must be the case, did the smallest quantity of elastic air exist in it.[69]

2. When the Doctor asserts that the dark colour of the venous blood is owing to the carbon it contains, he is in the first place chargeable with the error of former chemists, who supposed that every thing which could be extracted from any substance by fire, existed previously in it, in that very form in which it is extracted by the fire; and in the second place he speaks entirely at random, without even a shadow of proof. Nay, he himself tells us, that he has repeated two of Dr. Priestley’s experiments, which in the clearest manner demonstrate, that neither the addition nor the abstraction of carbon, or any thing else, give this dark colour to the venous blood. “A small glass tube (says he) filled with arterial blood, of a bright vermilion, was sealed hermetically,[70] and exposed to the light. The blood changed its colour by degrees, and in six days became black as venous blood. The same experiment was repeated, with this difference only, that the tube was exposed to heat, and not to the light. The blood became black in a shorter time.” In these experiments it is plain, that if the blood contained oxygen at first, it did so at the last; the same with regard to carbon. How came it then to pass, that without either evaporation of the former, or addition of the latter, the change should be produced? If the oxygen imbibed by the blood in the lungs was sufficient to produce the red colour, why did it not preserve it? The case here is precisely similar to what happens with the calx of silver. When that metal is dissolved in aqua fortis, and again reduced to a solid form, it appears as a white powder, and will preserve its colour if carefully kept from the light; but if a vial be filled with it, and exposed to the sun, that side on which the light falls will in a short time become black, and this though the vial has been ever so carefully sealed.[71] Formerly, chemists had a method of accounting for this appearance, as well as that of the venous blood, by what they called the evolution of phlogiston: but now that the very existence of phlogiston is denied, we are deprived of this resource. But, whatever words we may use, it is plain that in neither case have we any ideas affixed to them which can make the matter at all more intelligible than it was before. But with regard to the blood, we are at a considerable loss to understand what the natural colour of it is; and indeed the question can only be determined by examining the blood of a fœtus which has never breathed. If the arterial blood of such a fœtus be of a dark colour, resembling that in the veins of a grown person, we must look upon this to be natural to it, and we may as well inquire why a rose is red, or an iris blue, as why the blood is of a dark, and not of a bright red. But, if we find this dark red change to a bright scarlet in the arteries, as soon as the child has breathed, we have as much reason to conclude that the air occasions this superior redness, as that an acid is the cause of a red colour in the syrup of violets, or an alkali of a green colour in the same. Experiments are yet wanting to determine this matter. Mr. Hunter has observed that “in such fœtuses as convert animal matter into nourishment, they most probably have it (the colour of the blood) influenced by the air, such as the chick in the egg, although not by means of the lungs of the chick, we find the blood, in the veins of their temporary lungs, of a florid colour, while it is dark in the arteries.”—The probability therefore is, that the blood is naturally dark; by the elastic principle of the oxygen that it is rendered brighter; and that, this elastic principle being expended in the course of circulation, the fluid reassumes its original colour.

3. Though enough has already been said to evince that the superior redness of the arterial blood is derived from oxygen gas, we shall still quote two instances from Mr. Hunter’s Treatise on the Blood, which set this forth in the clearest manner; and these instances are the more remarkable, because they demonstrate the phenomena not of the dead, but of the living body. 1. A gentleman in an apoplexy, who seemed to breathe with great difficulty, was bled in the temporal artery. The blood flowed very slowly, and for a long time. It was as dark as venous blood. He was relieved by the operation; but, on opening the same orifice in two hours, the blood flowed of the usual florid colour. 2. A lady in an apoplexy was treated in the same manner, and Mr. Hunter observed, that when she breathed freely, the blood from the temporal artery assumed a bright red colour; but when her breathing was become difficult, or when she seemed scarce to breathe at all, it resumed its dark colour, and this several times during the operation.

4. Respiration is not, as Dr. Girtanner says, a process similar to the combustion and oxydation (the calcination) of metals. Some of these by calcination, and all of them in the opinion of Dr. Girtanner, unite with the condensable part of the oxygen contained in the air, while the elastic part is dissipated in flame or heat. The reverse of this takes place in breathing; for here the elastic part of the oxygen unites with the blood, and makes it warm, while the condensable part, uniting with certain particles to be thrown off from the body, passes away in fixed air. Thus the process of respiraton does not resemble the calcination of a metal (at least according to our author’s opinion of that operation) but rather the inflammation of some combustible substance; for in both cases a certain quantity of carbon is found to be united with the basis of oxygen in the atmosphere, and thrown off from the place of combustion; and thus a quantity of fixed air is produced from every burning substance. Just so is it with respiration. If the condensable part of the oxygen combined with the blood, then no fixed air could be produced; or if any part of the oxygenous base was absorbed, it must certainly be known by a proportional deficiency in the quantity of fixed air produced. But there are no experiments made with accuracy sufficient to determine this point. It is true that many very able physiologists, as Borelli, Jurin, &c. have been of opinion, that part of the air is absorbed in respiration; but when we come to particulars nothing can be determined. Dr. Hales by experiment found the quantity absorbed to be a sixty-eighth part of the whole quantity inspired; but, on account of supposed errors, he states it only at an hundred and thirty-sixth part. Between these two the difference is so enormous, that we know not how to draw any conclusion from them. The French chemists are more decisive, and agree pretty well with one another. Chaptal calculates it at three hundred and fifty-three, and La Metherie at three hundred and sixty, cubic inches in an hour. Allowing these experiments to be just, the next question is, what part of the air is absorbed. Lavoisier says, that it is the oxygenous base, or the same with that which is absorbed in the calcination of mercury. But how comes he to know this? Surely not in the same way that he determines the absorption of it by mercury. In the latter case he takes a certain quantity of mercury, includes it in another known quantity of oxygen air, and heats the metal by means of a burning-glass or otherwise: the consequence is, that the air is absorbed, the mercury loses its fluidity, and is increased in weight. The metal gains the whole weight of the air absorbed; and, by another process, all the air and all the metal, or very nearly so, may be obtained in their original form. This experiment is so decisive, that nothing can be said against it with any shadow of reason; but who hath made, or who can make, similar experiments with the blood of a living man? Such experiments indeed might be made, if insensible perspiration did not stand in our way. Common atmospherical air is about eight hundred times lighter than water. A cubic inch of distilled water, according to Dr. Kirwan, weighs two hundred and fifty-three grains and a quarter. Oxygen air is somewhat lighter than common air: we shall therefore suppose that six hundred inches of it are equal to an inch of water. If then the blood absorb three hundred and sixty inches of air in one hour, it will in twenty-four hours have absorbed eight thousand six hundred and forty inches, equal in weight to fourteen inches of water and two fifths, which according to Dr. Kirwan’s estimate is between seven and eight ounces. But the quantity of matter insensibly perspired in that time is so much greater, that no calculation can be made. Here is one mode of determining the quantity of oxygen inspired totally impracticable in the human body, though quite easy and practicable in the case of mercury. The other mode of determining it by the expulsion of oxygen from the blood is equally impracticable. Dr. Girtanner indeed has expelled oxygen from flesh; but we know not in what proportion, nor can we determine whence it came. With regard to this last, indeed, there are two sources allowed by Drs. Beddoes and Girtanner themselves; viz. the absorption of oxygen by the lungs, and the quantity taken in with the aliment. A third source was also manifest from Dr. Girtanner’s experiments; viz. absorption from the atmosphere; for, by exposure to the atmosphere, flesh, which had once parted with its oxygen, became again impregnated with it. In this case therefore we must acknowledge that the uncertainty of the absorption by the lungs must be extremely great. A certain quantity of oxygen is undoubtedly thrown out in fixed air. How are we to determine this quantity? Certainly not by the first reverie that happens to occupy our imagination. It is a problem, the solution of which must be attended with the utmost difficulty. We must know, in the first place, how much oxygen was contained in the air inspired. In the second place we must know the quantity of fixed air expired. In the third place we must exactly know the proportion of oxygen contained in the fixed air thrown out by the breath. In the fourth place we must determine whether, by the conversion of oxygen into fixed air, any change is made in its bulk. For, if this shall be found to be the case, we should be led to suppose an absorption or augmentation of air when no such thing took place. This point therefore ought to be determined with the utmost accuracy. In the fifth place we must exactly know how much azote, septon, phlogisticated air is contained in the atmosphere inspired, and likewise in that expired. In the sixth place, we must be assured that there are no other fluids in the atmosphere capable of being absorbed by the lungs, excepting oxygen and azote. Whether there are any others or not, hath not been determined. From an expression of Dr. Fordyce, he would seem to be skeptical on the subject. “The atmosphere (says he) is found to consist of various vapours, of which air, or, as it has been called, pure air, or respirable air, (oxygen air) forms at present about a fourth. Gas (probably fixed air) forms some part;[72] but the greatest part consists of one or more vapours, which, without any positive quality, but from that indolence which makes mankind in their researches attempt to find a resting place, have been considered by many chemists as one individual species, under the names of phlogisticated air,” &c. In the seventh place we ought to know what quantity of pure oxygen, unconverted into fixed air, or whether any such, is thrown out by the breath. That a quantity of this kind of air is really thrown out, is probable, because we can blow up a fire with our breath, and by a blow-pipe excite a most intense heat, capable of melting the most refractory metals, platina excepted. It is true that the eolipile, by the mere conversion of water into steam, will blow up a fire also; though, if the access of external air be denied, the blast of the eolipile will put the fire out. Probably the breath would do the same; but even this cannot be accounted a decisive proof of the oxygen being totally exhausted; for the moist vapour with which the breath abounds may extinguish the fire, even though some small quantity of oxygen should remain in it. It is not, however, our business at present to enter minutely into such discussions. From what has been already said, it is evident, that the absorption of oxygen by the blood, instead of being indubitably established, is of all things the most uncertain; the requisites for determining it being absolutely beyond the investigation of any person, however accurate. We may indeed, with great labour and trouble, determine that some part of the air is absorbed in breathing; but what that part is, we are unable to discover from any chemical investigation. The opinion of the simplicity of metals, and their being reduced to a calx by the adhesion of oxygen, has been so implicitly, and in a manner universally, received, that it has given a new turn to physiology, so that, by a kind of analogical reasoning, the human body has been reduced to a mere chemical apparatus, the operations of which may be calculated as we can do the event of experiments in a laboratory. But, after a very long and tedious contest, Dr. Priestley seems at last to have overthrown this doctrine of oxygenation, even in the inanimate parts of the creation; so that we can much less apply it to the doctrines of life and animation. His experiments are published in the third number of the Medical Repository, volume II, and fully demonstrate, that, though mercury absorbs oxygen during calcination, this is not the case with all metals; that in many cases the oxygen will unite with other substances in preference to the metal, which last is nevertheless reduced to a calx as though it had united with the oxygen; that in many cases the addition of weight gained by the calx is owing to mere water, &c. He has likewise shown that phlogisticated air (azote) is not a simple substance, as has been taught by the new chemists, but consists, as well as fixed air, of an union of oxygen with carbon, or at least with the black matter of burnt bones, with which he made the experiment. These aerial fluids therefore being so easily convertible into one another, and the uncertainty of the changes in bulk which may occur in consequence of these conversions so great, it is impossible to say whether a portion of the atmosphere in substance, i. e. both oxygen and azote, is absorbed, as physicians formerly supposed; or whether a portion of oxygen air alone be absorbed, as Dr. Beddoes supposes; or whether only the elastic principle itself is absorbed, and the diminution in bulk made in consequence of the conversion of oxygen into fixed air; I say, these matters depend on circumstances so much beyond the reach of our senses, that if we come to any probable conclusion upon the subject, it must be by analogical reasoning from other known facts, not from experiments made directly upon the living body; which, in their own nature, must, always be extremely vague and uncertain.

5. That, during the circulation, the blood charges itself with carbonic hydrogen air, is an assertion which cannot be easily admitted. It has already been observed, that, by the air-pump, venous blood does not appear to contain any elastic fluid whatever; and it is also certain, that animals cannot bear any quantity of air injected into their veins. Dr. Girtanner himself tried several kinds, and all of them proved fatal. Having injected a considerable quantity of oxygen air into the jugular vein of a dog, the animal raised most terrible outcries, breathed very quickly, and with the utmost difficulty; by little and little his limbs became stiff, he fell asleep, and died in less than three minutes. On injecting into the vein of another dog a small quantity of phlogisticated air, the animal died in twenty seconds. With carbonic acid gas (fixed air) a third dog died in a quarter of an hour. A fourth was killed in six minutes by nitrous air.[73] From these experiments, had no others ever been made on the subject, it seems very probable, that no species of air can be safely admitted into the blood in its elastic state. If any such therefore should naturally be produced in the body, it must either be instantly thrown out, or disease must ensue. Such objections to the Doctor’s theory are so natural, that we might have thought he would have foreseen and provided against them. Instead of this he grounds the whole upon such slender evidence as could not be admitted in the most trifling matter. “An incision (says he) was made in the jugular vein of a sheep, and the blood which came from it was received into a bottle filled with nitrous air. When the bottle was half filled, it was closed. The blood coagulated immediately, and a separation of a great quantity of blackish serum took place. The day after, on opening the bottle, a very strong smell of nitrous ether (dulcified spirit of nitre) was perceived, the nitrous air having been changed in part into nitrous ether by the carbonic hydrogen gas of the blood. This experiment proves, beyond a doubt, that the venous blood contains carbonic hydrogen air; and that this air is not very intimately mixed with it, but may be expelled with the greatest ease.”

On reading the Doctor’s account of this experiment; it must be very obvious, that, however decidedly he may be of opinion that it proves beyond a doubt the existence of hydrogen air in the venous blood, yet there is not one solid reason; from what he says, for supposing any such thing. How can any man determine from the mere smell of sheep’s blood taken out of the body of the animal, and mixed with a poisonous vapour, what is the composition of human blood in the living body? In the case of any substance suspected to contain elastic air, the air-pump will always afford an experimentum crucis. But we know that venous blood does not yield any elastic vapour by the pump: if instead of blood, however; we should fill a portion of vein with beer, cyder, or other fermented liquor, it would instantly discover, by its swelling up, that it really contained air in an elastic state. If then from the tumefaction of the vein when filled with fermented liquor we conclude that the latter contains fixed air, why should we not, from the non-tumefaction of it when filled with blood, conclude that the vital fluid contains no air? If Dr. Girtanner was so well assured that the venous blood contains hydrogen air, he ought to have expelled some of it from a portion of the blood, noted the difference between the blood which had lost its air, and that which had not, and then, by adding the air to it again, restored the blood to its former state. Nothing less then recomposition can prove the truth of a chemical analysis; as division can only be proved by multiplication, or multiplication by division.

From all that has been said, we may fairly conclude, that no proof can be brought sufficient to prove the existence either of oxygen air or any other species of aerial fluid, in its elastic state, in the blood. Neither can we prove that any part of the condensable part of oxygen air is received by the breath in the lungs. It is, however, probable that this condensable part may be received into the stomach with our food; that having passed through the various channels of circulation, and arrived at last at the surface, it there resumes its aerial nature by combining with the superfluous heat of the body, and is evaporated through the pores of the skin by insensible perspiration. The aerial vapour which passes off by these pores indeed has been discovered to partake of the nature of fixed air; but we know that this species of gas always contains the basis of oxygen, being indeed composed of it; and whether the oxygen be taken into the body in its pure state or not, the result would undoubtedly be the same; for an union would be formed between it and the carbonic particles to be thrown off from the body. But thus we can never suppose the basis of oxygen or any other air to be a permanent part of the composition of our bodies; nor can the quantity of it be augmented by breathing any kind of air. The readiest way to increase the quantity seems to be by drinking fermented liquors. Thus, if the body is too hot, the superfluous heat will have a proper subject to act upon, viz. the condensable part of the fixed air; and hence we may perhaps account for the very grateful and cooling sensation produced by drinking these liquors in some diseases. With respect to the existence of carbon, charcoal or hydrogen in the blood, it is probable that it exists in equal quantity at all times, being indeed the fundamental material of the whole body, and probably only a modification of that dust from whence man was originally taken.[74] When the blood therefore grows very black, when the teeth are covered with a black sordes, the hands become foul, &c. we may say, indeed we too surely feel, that, in such cases, there is a propensity in the body to return to its original state of dissolution; but there is not one solid reason for supposing the proportion of its materials to be varied; that there is a collection of oxygen in one part, hydrogen in another, or in short that nature can admit of any such disproportion taking place.

6. We must now consider Dr. Girtanner’s account of the origin of animal heat, which is, that, “during the distribution of the oxygen through the system, the heat which was united with this oxygen escapes; hence the animal heat;” and, “that the great capacity of the arterial blood for heat is owing to the oxygen with which it is united in the lungs.”—This leads us to consider in a more particular manner the doctrine of heat, a subject hitherto much less investigated than the importance of the subject requires. What little we do know of this matter seems to be almost entirely owing to Dr. Black, who hath discovered some very remarkable phenomena unknown to former philosophers. His discovery here, as in that of fixed air, was accidental. Making experiments on the water of different temperatures, he found that the mixture would always be an arithmetical mean betwixt the two quantities mixed. Thus, on mixing water at 50 degrees with an equal quantity at 100, the temperature of the mixture would be 75 degrees; but if instead of using water only he took snow or ice for one of the quantities, the mixture was no longer an arithmetical mean betwixt the two temperatures, but greatly below it; so that a quantity of heat seemed to be totally lost and in a manner annihilated. His attention was engaged by this unexpected phenomenon, and, prosecuting his experiments, he found that, when water was converted into ice, it really became warmer than it was before; and, by keeping the fluid perfectly still during the time that cold was applied, he was able to cool it to 27 degrees of Fahrenheit’s thermometer, which is five degrees below the freezing point; but on shaking this water so cooled, it was instantly converted into ice, and the thermometer rose to 32. On reversing the experiment he found that mere fluidity in water is not sufficient to melt ice. A considerable degree of heat is necessary; and even when this is previously given to the water, the whole becomes as cold as ice by the time that the ice is melted. The result of his experiments in short was this: Water, when frozen, absorbs an hundred and thirty-five degrees of heat before its fluidity can be restored: that is, supposing a pound of ice at the temperature of 32 to be mixed with a pound of water at the temperature of 32, by adding 135 degrees, so that the temperature of the water is augmented to 167, the ice will indeed be melted, but the temperature of the whole quantity of liquid will be reduced to 32. In this case therefore the heat manifestly assumes two different modes of action: one in which it acts internally upon the substance of the body, without being sensible to the touch, while in its other state it hath no effect upon the internal parts, but affects bodies on the outside. The former state therefore the Doctor distinguished by the name of latent, the latter by that of sensible heat.

The same theory was applied to explain the doctrine of evaporation, and that in the most decisive and satisfactory manner. The Doctor found, that, in the distillation of water, much more heat was communicated to that in the worm-tub of the still, than could be supposed necessary to raise the water distilled to 212 degrees, which is the utmost that water can bear. In prosecuting the experiment he found the quantity of heat absorbed by the water, when raised into vapour, truly surprising; no less than a thousand degrees; an heat more than sufficient to have made the whole quantity of fluid that came over red hot. Some objections, however, were made to this theory, even by the Doctor’s friends. Mr. Watt, particularly, though he could not deny the theory derived from Dr. Black’s experiments, yet suggested one, which, had it proved successful, would have overthrown the whole. It was this: Let water be distilled in vacuo, where it boils with a heat of 97 degrees, and the operation must be carried on with much less fuel, and with much greater ease, than in the common mode. It was said that, in this experiment, Dr. Black was equally concerned with Mr. Watt; but, in a personal conversation with the Doctor himself, he assured me that he had no farther concern than foretelling that the experiment would not succeed, which it seems did not. The event was as follows: Mr. Watt, determining at all events to try the experiment, caused to be made a copper retort and receiver, joined together in one piece. In the receiver he pierced a small hole, and, heating both retort and receiver, plunged the latter into cold water. The consequence was, that a considerable quantity of water entered the vessel, and was easily poured back into the retort, as a subject for distillation. A fire being now applied, the water was soon raised into steam, which filled both retort and receiver, and in a great measure expelled the external air. The small orifice in the receiver being now closed, and the receiver itself plunged into cold water, the distillation went on in vacuo; for, as soon as any of the steam was condensed, the space which it had occupied (according to Dr. Black one thousand and sixty-six times more than the original water) was become absolutely empty, and more steam, rarefied, not by any quantity of sensible heat, but merely by that which it contained in a latent state, would occupy the place of the former. The event of the experiment showed the truth of Dr. Black’s theory. The water boiled, and steam was raised as well as if access had been given to the air; but with this difference, that the upper part of the distilling vessel was never heated above what the hand could easily bear. With the water in the cooler it was quite otherwise. It became hot as usual, and, by the quantity of heat it received, plainly demonstrated that the vapour, though destitute of most of its sensible heat, yet contained an immense quantity in a latent state. The saving of fuel therefore in the practice of distillation, which was Mr. Watt’s object in making the experiment, was quite trifling, and not equal to the trouble of filling the retort with liquid.

The doctrine of latent heat thus established, furnished a solution of many phenomena which could not formerly be explained in a satisfactory manner. Thus the melting of all kinds of substances was found to be owing to an absorption of heat, while their condensation was attended with the contrary. Fluidity in all cases was explained on the same principle; and the more heat that was absorbed, the more fluid the matter became. Thus water, when in a condensed or solid state, absorbs 135 degrees of heat before it becomes fluid. A thousand degrees more convert it into vapour, and at last, by passing through the intense heat of a glass-house furnace, it is converted into a brilliant flame, and augments the heat of the furnace to a great degree. Hence the practice in glass-houses of throwing water into the ash-hole, the vapour of which, by passing through the burning fuel, makes the furnace much hotter than it was. In a similar manner were explained the phenomena of crystallization, the ductility of metals, the heat produced by hammering them, and the hardness produced by the operation, as well as the operation of annealing, &c. One other phenomenon, a very curious one, shall be noticed, on account of its being connected with the subject of this treatise. It is this: Let a small vessel filled with vitriolic ether be put into a larger one of water, and both included in the receiver of an air-pump. On exhausting the air, the ether boils, and is converted into vapour, while the water freezes. This shows that heat does not always act equally upon surrounding bodies, but has a tendency to enter some in preference to others; and from other experiments it appears, that this property has a considerable connexion with the density of the bodies concerned.

Thus one step was gained, and it was universally admitted that heat, in some cases, entered bodies, and in others was thrown out of them; but now the question arose, What is heat; and by what laws is it regulated, or from what source is it derived? Here Dr. Black himself was at a loss; for, as he supposed cold to be a mere non-entity, and only to consist in a comparatively smaller degree of heat, some phenomena occurred which would not easily admit of solution upon such an hypothesis. With these Dr. Black did not meddle much, but others were bolder. Dr. Irving, Professor of Chemistry at Glasgow, undertook to explain the whole mystery of latent heat upon the single principle of attraction. One of the most puzzling phenomena in the way of Dr. Black’s theory had been, that in some cases heat and cold seemed to repel each other, and a very remarkable instance of this was, that, in the morning, a little before sunrise, when the rays of light pass through the atmosphere, a little above the surface of the earth, the air then becomes manifestly colder than even at midnight. Dr. Irving’s explanation of this was, that the sun’s rays attracted heat from the atmosphere, and thus rendered it colder. Such at least was the explanation given in an inaugural dissertation by Dr. Cleghorn, one of Dr. Irving’s scholars; for the Doctor himself delivered his opinions only to them. In other cases he supposed that different substances had different capacities for receiving heat; and, of consequence, should the form, or rather the internal constitution, of the body be changed, the capacity of it for receiving heat must also be changed; and as an attraction subsists, or is supposed to subsist, between heat and all other substances, it is plain that while this attraction subsists, if the capacity of any substance for receiving heat be augmented, it will imbibe much more than it would have done had its former constitution remained. Thus water in its liquid state contains a certain quantity of heat; we may therefore say that water has a capacity for receiving heat equal to one to ten, or what we please. Vapour has a capacity for containing heat ten times greater than water. Water therefore, when converted into vapour, will imbibe ten times the quantity of heat that the water contains; and, again, on being re-converted into water, the capacity becoming what it was before, the superfluous quantity must be thrown out, as in Dr. Black’s experiments. In like manner, when a metal is melted by the fire, the capacity of it for receiving heat is changed: of consequence a great quantity is imbibed, and again expelled by the change of capacity which takes place on its becoming solid; and thus, from the change of capacity, in different substances, every phenomenon was solved.

This doctrine of capacities did not give general satisfaction. Dr. Black himself said of it, that it was neither probable nor ingenious;[75] notwithstanding which, it continued to be received, and even very generally adopted. Dr. Crawford, so well known for his writings on this subject, has adopted the idea, and Dr. Girtanner, in the passage above quoted from him, appears to be of the same opinion. The doctrine, however, had several opponents, among whom were the Monthly Reviewers. In their account of Nicholson’s First Principles of Chemistry, they express themselves in the following manner: “We only wish, that, in the doctrine of heat, he had avoided, which he might easily have done, Dr. Crawford’s idea of bodies having different capacities for heat. In the melting of ice, for instance, a quantity of heat is absorbed, without any increase of the temperature, that is, without making the water sensibly warmer than the ice before its liquefaction; which is said to be owing to the water having a greater capacity for heat, or being able to hold more of it, than the ice; and, in like manner, when converted into vapour, its capacity is further increased, or it can hold more still. This appears to us a very unchemical, and a very inadequate idea of the matter: for, admitting water to have a greater capacity than ice, how is the change from one state to the other to be effected? Can the properties which a body is found to possess, after a change has taken place, be assigned as a cause of the change itself? Or will it be said, that the heat first enlarges the capacity, and then hides itself in that capacity so enlarged? We should think it much better to say, consonantly with the phenomena of other combinations in chemistry, that a certain quantity of heat, uniting with the ice, first liquefies it, as a certain quantity of acid only neutralizes an alkali; that if any surplus quantity must be introduced, that surplus, remaining free and uncombined, must act and be sensible as heat in the one case, and acid other; and that different bodies require different quantities of heat or acid to be combined with them, for producing the changes in question.”[76]

Thus the Reviewers, as well as others, reasoned a priori, and several facts were adduced to prove that no such changes in capacity could take place. But however strong the arguments adduced, or however plain the experiments might be, little or no notice was taken of them, and the enlargement or diminution of capacities has been repeated, seemingly by rote, from one author to another, without the least inquiry or investigation. Dr. Girtanner indeed says that “the oxygen united with the arterial blood in the lungs” is the cause of the great capacity of the arterial blood for heat. But this is assigning a very doubtful cause for a very doubtful effect. He ought to have proved in the first place that arterial blood really has this capacity; for its being hotter than the blood of the veins, only shews that it parts with more heat to surrounding bodies than venous blood does; which is a proof that it contains less heat, if there be any difference, than that of the veins. But the truth is, that the capacity for containing heat depends neither on the oxygenation nor hydrogenation of a fluid, but upon its density. The more fluid and the more easily expansible into vapour that any substance is, the greater quantity of heat it is capable of containing, and vice versa. This has been fully ascertained by Mr. William Jones, an English clergyman, whose observations on the generally received system of philosophy contain many particulars worthy of attention. From his experiments it appears that a piece of red-hot iron, thrown into water, imparts much less sensible heat to it, and is itself much more effectually quenched, than by throwing it into an equal quantity of quick-silver of the same temperature with the water. As the quick-silver therefore becomes much hotter to the touch than water does upon throwing a piece of red-hot iron into it, and as the iron itself is much more imperfectly quenched by the metal than by the water, it follows that the latter is capable of containing much more heat than the former. But such experiments are not applicable to the blood. Though that of the arteries may be somewhat hotter than the venous blood, yet the reason is obvious. The heat is communicated directly to the arterial blood in the lungs; but during the circulation a part of it evaporates, and the farther distant any part is from the lungs, the more cool will the vital fluid be, without regard to any alteration of capacity, which indeed never can be shown to exist.

But the most decisive experiments against any supposed alteration in the capacities of bodies for containing heat are those lately tried by Count Rumford, and related in the Philosophical Transactions for 1798. His attention to this subject was engaged by observing the great degree of heat acquired by a brass gun during the time of boring it,[77] and still more by the intense heat (much greater than that of boiling water) of the metallic chips separated from it by the borer. From a consideration of these things he was naturally led to the following inquiries. “Whence comes the heat actually produced in this mechanical operation? Is it furnished by the metallic chips which are separated by the borer from the solid mass of metal? If this were the case, then, according to the modern doctrine of caloric, the capacity for heat of the parts of the metal so reduced to chips, ought not only to be changed, but the change undergone by them be sufficiently great to account for all the heat produced. But no such change had taken place; for I found, that by taking equal quantities by weight of these chips, and of thin slips of the same block of metal, separated by means of a fine saw, and putting them at the same temperature, that of boiling water, and putting them into equal quantities of cold water (that is to say, at 59 1/2 of Fahrenheit) the portion of water into which the chips were put, was not, to all appearance, heated either less or more than the other portion in which the chips were put.”

From this experiment, several times repeated with the same result, Count Rumford inferred, that the heat could not possibly have been furnished at the expense of the latent heat of the metallic chips. He then proceeded to ascertain “how much heat was actually generated by friction, when a blunt steel borer being so forcibly shoved (by means of a strong screw) against the bottom of the bore of the cylinder, [of the machine in use] that the pressure against it was equal to the weight of about ten thousand lb. avoirdupois, the cylinder being turned round on its axis (by the power of horses) at the rate of about thirty-two times in a minute.” In this experiment the metallic dust or scaly matter detached from the cylinder by the borer weighed only 837 grains troy; but, says the author, “Is it possible that the very considerable quantity of heat produced in this experiment (a quantity which actually raised the temperature of above 113 lb. of gun-metal at least 70 degrees of Fahrenheit’s thermometer, and which of course would have been capable of melting 6 1/2 lbs. of ice, or making near five pounds of ice-cold water to boil) could have been furnished by so inconsiderable a quantity of metallic dust, and this merely in consequence of a change of its capacity for heat? As the weight of this metallic dust (837 grains troy) amounted to no more than one 948th part of that of the cylinder, it must have lost no less than 948 degrees of heat to have been able to raise the temperature of the cylinder one degree; and consequently it must have given off more than sixty-six thousand, three hundred and sixty degrees of heat to have produced the effects which were actually found to have been produced in this experiment.”

It was next considered whether the air did not contribute to the generation of this heat; and our author determined that this could not be the case; because the quantity of heat generated was not sensibly diminished when the free access of air was prevented. From another experiment it appeared that the generation of the heat was neither prevented nor retarded by keeping the apparatus immersed in water. Here the friction generated so much heat, that in one hour the temperature of the water surrounding the cylinder was raised from 60 to 107 degrees of Fahrenheit. In half an hour more it was raised to 142; at the end of two hours to 178; at two hours 20 minutes to 200; and in two hours and a half it boiled.[78] On the whole, Count Rumford concludes, that “the quantity of heat, produced equably by the friction of the blunt borer against the bottom of the hollow metallic cylinder, was greater than that produced equably in the combustion of nine wax candles, each three quarters of an inch diameter, all burning at the same time with a clear, bright flame.” From all these experiments, however, our author does not draw any certain conclusion. “What is heat? (says he.) Is there any such thing as an igneous fluid? Is there any thing that can with propriety be called caloric? The heat produced, in the author’s experiments, by the friction of two metallic surfaces, was not furnished by small particles of metal, detached from the larger solid on their being rubbed together. It was not supplied by the air, because the machinery in three experiments was kept under water, and the access of atmospherical air completely prevented. It was not furnished by the water which surrounded the machinery, because this water was continually receiving heat from the machinery and could not at the same time be giving to and receiving heat from the same body; and because there was no chemical decomposition of any part of this water.” At last he observes, that the source of this heat, whatever it is, must evidently be inexhaustible, adding, that “any thing, which any insulated body, or system of bodies, can continue to furnish without limitation, cannot possibly be a material substance; and it appears to me to be extremely difficult, if not quite impossible, to form any distinct idea of any thing capable of being excited and communicated, in the manner the heat was excited and communicated in these experiments, except it be MOTION.”

On this last paragraph, however, it is obvious to remark, that the whole force of the argument rests upon an insinuation, that the cylinder and borer were insulated, or cut off from all communication with any other material substance. Had this been the case, then no doubt it would follow that an endless supply of any thing material could not be furnished by them; but if, as Dr. Boerhaave and many other learned and intelligent persons have supposed, fire be an element universally present, and which becomes sensible to the touch only in consequence of a particular mode of action, it will follow, that no substance in nature can be insulated with respect to it; but, in whatever place, and for whatever length of time, any substance shall be affected in such a manner as to agitate this fluid, there we shall perceive a production of heat without limitation, even though heat itself be no more than the action of a fluid essentially material, though invisible to us.

Considerations of this kind occurred long ago to the writer of this treatise, when by the nature of his employment it was necessary for him to speculate upon these subjects. It could not then but appear to him that the theory of Dr. Black was far superior to any that had been published. The opinion of those who supposed fire to consist in the vibratory motion of the particles of solid bodies, seemed altogether untenable. It is impossible to explain the phenomena of heat upon ordinary mechanical principles, because, with respect to all terrestrial substances, heat constantly appears as an agent, while they are merely passive; and no man can explain the nature of a cause from its effect. Thus one of the most obvious effects of heat is expansion, or enlargement of bulk, in such bodies as are heated. But if from this fact we infer that the parts of elementary fire are repulsive of one another, our reasoning is certainly erroneous. In like manner, when we are not sensible of heat, we are not authorised to conclude that it is not present; for Dr. Black has demonstrated that it may be present in very great quantity, though indiscoverable either by our senses or by a thermometer.

But, with regard to the theory published by Dr. Black himself, it is evident that, though one part of it rests on the solid basis of experiment, the other is founded entirely upon hypothesis, and that too an hypothesis which cannot admit of being proved by any experiment, viz. that cold is a mere negative, and hath no real existence in nature. Among many phenomena which militate against this opinion, the following experiment of M. Geoffrey seems to be the most remarkable. He took a small bason filled with water, and set it on a support in the middle of a large tub of water, in such a manner that the temperature of the water in the tub might communicate itself to that in the bason. This being ascertained by a thermometer placed in the bason, he threw a quantity of burning coals into the tub. The effect of this, on the supposition that cold is a mere privation of heat, ought to have been, that the heat of the coals, communicated to the water in the large tub, would in a short time pervade the small bason, and affect the thermometer there. The latter would therefore rise; but instead of this it fell several degrees before it began to rise; for which it doth not appear that any other reason can be assigned than that the cold is partly repelled by the heat of the coals, and therefore, entering into the small bason of water, it causes the thermometer to sink previous to its rising. To the same purpose we may urge the phenomenon already taken notice of, viz. that the sun’s rays, when passing at some distance above the surface of the earth, cool the lower part of the atmosphere. The natural solution is, that the heat of the sun partly repels the cold downwards; and as for the doctrine of attracting heat from the atmosphere, Count Rumford has shown that this does not happen in a case where we might with much more probability expect it; not to mention the violence done to the common perceptions of mankind by supposing the sun’s rays, which are most evidently the source of heat, to have any occasion to attract heat from the atmosphere or any thing else.

Lastly, with regard to the capacities of bodies for containing heat, the doctrine appears to involve a radical error, of such enormous magnitude, that it is impossible to make any thing of it. This is no less than confounding the heat which flows out from bodies with that which they contain as an essential part of their composition, and which they cannot emit without being changed into some other form. Thus the capacity of aqueous vapour for containing heat, according to Dr. Black, is 1000 degrees; yet without decomposing the vapour it would have been impossible to have known this; for vapour is often extremely cold to the touch, and a thermometer immersed in it will sink greatly. In short, all that we can know about the capacity of bodies for retaining heat is, that they either continue to absorb it, or we may continue to force it into them, till they be reduced to vapour. It is doubtful whether they can receive more; for from the experiment with Papin’s digester, formerly mentioned, it appears that the additional quantity of heat, which the water was made to receive, very quickly left it as soon as the steam had room to expand.

But, to come to a conclusion upon this subject: If we will investigate the nature of heat, we must do it as in other cases, viz. by making the igneous fluid, caloric, or what we please to call it, the object of our senses; for we cannot reason fairly, or indeed come to any rational conclusion at all, by doing otherwise. In this investigation it is necessary to attend to the particulars mentioned by Count Rumford. The fluid must be omnipresent in its nature, infinite in its quantity, and equable, uniform and incessant in its action; as far as these epithets can be applied to any material being. There are only two fluids which we know that can answer to these characteristics. The one is the light of the sun, which pervades all the celestial spaces; the other the electric fluid, which penetrates every terrestrial substance. Both of these produce heat, unlimited in quantity, as well as in duration, provided their action be continually kept up. The mode in which both produce heat is exactly the same, viz. by converging into a focus; and the greater the quantity, the greater is the heat, and that without any limitation either as to intensity or duration. With regard to the solar rays, it has long been known that by concentration they would produce heat; nevertheless it was unaccountably doubted whether the rays themselves were the matter of heat. One objection to this was, that on the tops of high mountains the air is exceedingly cold, though the sun shines very bright. But this objection was founded upon an erroneous notion that, wherever the matter of heat exists, there we must feel it; which doth not follow any more than that wherever air exists there we must feel a wind blowing upon us. Wind is air in motion, and heat is a more subtile fluid in motion. One demonstration of this is, that, on the tops of the highest mountains, a burning lens or mirror will set fire to combustible bodies as readily as in the vallies at the foot of them. Neither has heat, properly so called, anything to do with air. The focus of a burning-glass will heat bodies in vacuo as well as in the open air; and Sir Isaac Newton has observed, that if a thermometer be included in the vacuum of an air-pump, it will acquire the temperature of the room nearly in the same time that another will when included in a similar glass without any exhaustion.

The science of electricity is but of late date; and most violent and hypothetical disputes have taken place concerning the nature of the fluid. Its luminous and burning properties naturally led a number of people to suppose that it was elementary fire; but this was opposed by others with as much violence as if there had been something criminal in the supposition. The opposition, however, was founded upon the same error with that about the solar light. It was imagined that wherever elementary fire existed, there heat must be felt; and it was especially urged, that electricity, though it produced light, did not produce any heat, except when it exploded with such violence as to penetrate the internal substance of bodies, agitating their particles, and by this agitation producing heat. It has now, however, been found, that the electric aura, as it is called, when made to converge in great quantity to the point of a needle, will heat it to such a degree as to set fire to gun-powder. This shows that heat is occasioned by the convergence of this fluid to a focus, and to its divergence from it. In the focal point, heat will always take place. From the experiments of Hauksbee, Beccaria and Priestley, it likewise appears, that electricity will render transparent the most opaque bodies, such as sealing-wax, pitch, &c. which even the most intense light of the sun cannot do. As to the intensity of the heat produced by it, experiments have shown, that it cannot be exceeded even by that of the most powerful mirror. Globules of gold have been vitrified, platina melted, and the most infusible substances reduced to glass, by means of the electric shock. From so many evidences, therefore, it appears to me impossible to conclude otherwise than that the light of the sun and the electric fluid are the same thing; and, according to the different modes in which they act, they produce the phenomena of heat and light in all their varieties, besides a multitude of other effects of which we cannot have any perception. We may indeed, if we please, suppose that some other thing exists which is heat itself, and that the light or electric fluid sets in motion, attracts, repels, or acts otherwise upon this unknown something; just as it comes into our heads to fabricate our system. But, until our senses can discover in some way or other this hidden substance, reason will always suggest that it has no existence. We may say that without such a supposition we cannot solve the phenomena of heat. But do we ever expect to solve these phenomena; or do we know all that the solar light and electric fluid can perform? If we do not know what they can do, neither do we know what they cannot; and the invention of other fluids must be accounted not only chimerical but useless.

But, to be more particular: on the subject of heat people have embarrassed themselves more with philosophical reveries than by any real difficulty, and rendered the matter more obscure than nature has made it. We have already observed, that by the convergence of light, or of electricity, heat is always produced. Here we can see the mode in which the fluid acts, viz. first by converging, and then diverging. When the light falls upon a solid body, it is evident, that if it be allowed to flow out as easily as it flows in, no internal agitation of the parts, or of any fluid contained in them, can take place. Transparent bodies therefore are never heated. Again, if the light be not allowed to enter the substance of a body, but is entirely reflected, the body cannot be heated; and hence it is very difficult to melt a polished metal even by a strong burning-glass. M. Macquer’s burning mirror, which vitrified flints, could not melt silver. But, when the light falls upon a body capable of allowing it to enter its substance, at the same time that it cannot get out without difficulty, it is plain that the force of the fluid will be exerted in order to overcome that difficulty; the body will be expanded in all directions; the fluid will be thrown out in the same manner, and the more that the internal action of the light prevails over that power by which the parts of the body cohere, the more will the phenomena of heat be perceptible.

Again, let us suppose that the etherial fluid enters the substance of any body capable of being dilated to a great degree, it is equally plain that the action of the fluid must for some time be directed only upon the internal parts, and consequently will be imperceptible on the outside. This then is called latent heat; and where the pressure on the outside balances that on the inside no heat will be perceptible to the touch. But by whatever means this balance is broken, heat will instantly be perceptible; and experiments show that the balance may be broken either by an increase of cold or heat. Thus, in the case of water, the internal pressure remains equal to the external, until the fluid is cooled to a few degrees below 32. The balance is then broken, and the internal action prevails; a quantity of what is called sensible heat escapes, and the water is converted into ice. Again, at the temperature of 32, little or none of the water evaporates; but by the addition of heat, by which the internal action of the subtile fluid we speak of becomes greater than the external, the water is converted into vapour; and it is remarkable that the same effect takes place on greatly augmenting the degree of cold; for the evaporation from ice, even in frosty weather, is found to be very considerable.

On the whole, from innumerable experiments it appears, that there exists in nature a certain invisible fluid, by the action of which, when diverging from a centre, heat is produced in the central point. By a certain other power this diverging force is limited, so that in some cases it is not perceptible beyond the surface of the body in which it acts, and then it is called latent heat. In other cases it is perceptible in a certain degree, and the degree in which it is perceptible hath been called the temperature or sensible heat of the body. On mixing different substances together it is found, that very often the proportions between the external and internal actions are varied. This has been already observed, when giving an account of Dr. Black’s discovery of latent heat, viz. that when snow and warm water are mixed together the temperature of the mixture differs very considerably from the arithmetical mean between the temperatures of the two substances employed. Dr. Crawford prosecuted the experiment further, and found that there were few substances which, on being mixed, did not shew a temperature different from that of the arithmetical mean between the temperatures of the two originally employed. This difference he unfortunately used as the foundation of a rule for determining the capacities of different substances for containing heat, and upon this erroneous principle has raised a superstructure, which upon no occasion can be of service to science, but must always produce obscurity and confusion wherever it is introduced.

With regard to the power which sets bounds to the expansion of the fluid acting as heat, it is natural to think that it can be no other than the same fluid acting in a contrary direction, or from a circumference towards a centre; and thus we shall always find that the same fluid, by limiting its own operations, may produce those phenomena which have been hitherto deemed so difficult of explanation. In what manner this limitation is in all cases effected, or indeed in any case, we cannot pretend to explain. It is sufficient to observe, that wherever there is a perpetual efflux of any thing, there must be also a perpetual influx at the same time, and in proportion to the one the other will be. These two are directly contrary to one another, and, as we suppose the fluid to be universal, it is evident, that if any part of it be put in motion in a particular direction, the rest will press towards that part where the motion is, in order to keep up the equilibrium. Hence we may easily account for the heat produced by percussion or by friction. By hammering a piece of iron, as Dr. Black justly observes, the fluid is forced out from between the parts of the metal. The emission of this fluid in all directions is heat itself; and no sooner is one quantity thrown out than another supplies its place with great rapidity, and so on, until the pressure of the rest in some way or other counteracts the emission of any more, and the heat ceases. Just so with friction. The heat produced by it is always in proportion to the pressure employed. By this pressure the parts of the two substances are forced into such close contact, that an agitation and emission of the fluid pervading their substance takes place. This agitation, as we have already noticed, is heat itself, and, as long as the friction is continued, more and more heat will be produced, without any limitation, as Count Rumford has observed.

Some bodies have a greater disposition than others to emit this subtile fluid; and these we say are naturally of a warmer temperature than others. The temperature is nothing else than the efflux of the fluid from them, continually kept up by the action of the surrounding fluid. By mixture with different substances the temperatures of various bodies may be changed; by some the influx, and by others the efflux, may be augmented. In the former case we say the body becomes colder, in the latter hotter, than before; and in not a few cases the agitation of the fluid becomes so great that the matter actually takes fire. In all these cases, however, we can discover nothing more than the bare fact, that so and so is the case. We know that the bodies do grow hot by the convergence of the etherial fluid towards them, and its emission from them; but why it should converge or diverge we know not.

Thus much with regard to heat in general. We must next consider another fluid which has very generally been accounted the source and fountain of heat, viz. air. This is indeed so much the source of heat in all our operations, that it was natural to think it the only one; but experiments have now determined that air itself is a mere creature of heat and light;[79] for, by employing these in a proper manner, airs or gases of all kinds have been produced. Thus, by exposing water in a glass vessel for some time to the rays of the sun, a quantity of very pure oxygen air may be obtained; by concentrating the sun’s rays upon charcoal, inflammable air may be had; and by distilling, with a strong heat, substances of various kinds, we may obtain a great variety of aerial vapours. From all this we may reasonably conclude that heat, attached to some other substance, dissolved in it in such a manner as to become invisible, forms the substance of air. Heat therefore being the agent in the composition of air, it is reasonable to suppose that it is the agent in its decomposition also, or in its transformation from one species to another, of which the conversion of oxygen into fixed air by combustion is an instance. When air is taken into the lungs the blood is warmed by the action of that invisible fluid, which has already given elasticity to the air. In consequence of a considerable quantity of this fluid being then converted from a latent into a sensible state, part of the elastic principle must be lost, and the air diminished in bulk. The reason why this must constantly take place is, that part of the heat evaporates from the surface of the body, during the course of circulation. Were it not so, the quantity thrown out by the lungs would be exactly equal to that which the blood received, and consequently there could be no diminution between the bulk of the air expired and that which was inspired; but, on account of the waste just mentioned, the blood must always receive somewhat more than it gives out by the breath. Thus, while the air we breathe continues the same, and the organization of the body is not changed, the natural operations will go on smoothly, and health will continue; but, as we have formerly observed, by an alteration of either of these, disease must ensue; and we must now endeavour, from the principles laid down, to examine the mode in which epidemic diseases, and particularly the plague, may be produced.

The air is so evidently connected with human life, that it has been from the earliest ages accounted the source of pestilential diseases, though, as none of the more obvious qualities of it, such as heat, cold, moisture, or dryness, appeared to be connected with them, they were generally supposed to proceed from the action of some unknown natural cause, or from that of the Deity himself. Some, however, have also been of opinion that plagues might originate from the obvious qualities of the air in conjunction with certain effluvia from putrid vegetable or animal bodies. Thus, in several plagues mentioned in ancient history, we find swarms of dead locusts, grasshoppers, the carcases of those slain in battle, crowded houses, and filth of all kinds, assigned as causes. This opinion was adopted by Dr. Mead, and he gives the following account of the origin of the plague in Egypt. “Grand Cairo is crowded with inhabitants, who for the most part live very poorly and nastily; the streets are narrow and close; it is situate in a sandy plain, at the foot of a mountain, which, by keeping off the winds that would refresh the air, makes the heats very stifling. Through the midst of the city passes a great canal, which is filled with water at the overflowing of the Nile; and, after the river decreases, is gradually dried up: into this canal the people throw all manner of carrion, filth, &c. so that the stench which arises from this and the mud together is insufferably offensive. In this posture of things, the plague every year preys upon the inhabitants, and is only stopped when the Nile, by overflowing, washes away this load of filth; the cold winds, which set in at the same time, lending their assistance by purifying the air.” He then proceeds to account for the plagues in Ethiopia in the manner above related, viz. by the prodigious swarms of locusts, which sometimes occasion a famine by devouring the fruits of the earth, and, when they happen to be cast by the winds into the sea, occasion a pestilence; the putrefaction being heightened by the intemperance of the climate, which here is so great that it is infested with violent rains for three or four months together; and it is particularly observed of this country, that the plague usually invades it whenever rains fall during the sultry heats of July and August. He next takes notice of what the Arabians say of the origin of the plague in Ethiopia, viz. that it is brought on by unseasonable moistures, heats, and want of winds. But, whatever truth may be in the account given of the Ethiopic plagues, the testimonies already produced in this treatise are sufficient to render it very doubtful, at least, whether the plague ever does originate in Cairo, or any other place in Egypt. Besides, if we once admit the existence of any thing as a cause adequate to the production of a certain effect, wherever that cause exists the effect ought certainly to follow, unless where we plainly perceive something which prevents its action. It is not fair reasoning to say that the action of the cause is prevented by something unknown, for we might as well say that this unknown something is the cause originally, and acts only upon certain occasions, of when it thinks proper. Now, if the filth of the canal of Cairo be the cause of the plague in that city, it ought to recur annually at the season when that filth exists in greatest quantity, and in the most putrid slate. Nevertheless we have the express testimony of Mr. Eyles Irwin, that at the time he was in Cairo there had not been any plague for seven years. The account he gives of it is a kind of contrast to that above quoted from Dr. Mead. “Misir al Kaira, says he, or the City of Anguish, so called from the frequent visits which it has received from the plague, but commonly called Grand Cairo by us, is situated in lat. 30 degrees 3 minutes N. on an artificial branch of the Nile. Old Cairo nearly faces the river; but the new city is removed above a mile from it, and approaches to the range of mountains which runs through Upper Egypt, and abruptly breaks off here. It is undoubtedly one of the finest cities in the east; which, from the present style of architecture that reigns among the orientals, is but a faint commendation. The houses are in general built of stone, and, being elevated to several stories, would make a grand appearance, notwithstanding the inelegance of their structure, were not the effect destroyed by the excessive narrowness of the streets. This is one of the causes to which the ingenious Dr. Mead ascribes the birth of the plague in this capital; but experience evinces that it arises from foreign and adventitious causes. There has not been a plague here these seven years; which is rendered more remarkable by the commencement of the Russian war at the date of its cessation. No one can account for this; though a year seldom passed by before without a visit from it.”[80]

From this it plainly appears, that, however these putrid effluvia may concur with other circumstances in producing the plague, they are by no means the only cause; otherwise not a single year could have passed in Cairo without a pestilence; and the very same thing we shall find to hold good in every other, let us choose for a cause what we will. In order to investigate this matter fully, we must now consider what causes have been assigned by physicians for other epidemical diseases; and here, to avoid prolixity, we shall chiefly confine ourselves to those enumerated by Dr. Fordyce as the causes of fever; a gentleman whose very extensive experience must give the greatest weight to his testimony.[81] The principal causes assigned by him are,

1. Infection, or “a peculiar matter generated in the body of a man in fever, which is carried by the atmosphere, and applied to some part of the body of a person in health, and which causes fever to take place in him.” That such a cause exists, he proves from observing that “of any number of men, one half of whom go near a person ill of a fever, and the other half do not, a greater number of the former will be infected, in a short period afterwards, than in those who do not.” He says he has known, in such circumstances, seven out of nine infected with the disease. This infection is not discoverable by smell or any other organ of sense; neither can the greatest attention to cleanliness disarm it of its malignity. Of this the Doctor says that he has known instances; nay, of a person going into a room where a feverish patient was, and bringing with him the infection, which was communicated to others in the room to which he came. He owns, however, that by allowing the air to stagnate in which feverish patients are, the infection will become extremely violent and fatal. This may naturally be supposed, even without having recourse to putrid effluvia; because, independent of these, the imperceptible infectious matter itself will undoubtedly be accumulated in the atmosphere of the room, and act more powerfully than it could have done had it been partly carried off and diluted by attention to cleanliness and ventilation. He also says, that “when a number of persons live in a small space, supposing even that they are kept as clean as possible, it happens frequently that fever arises in some, often in many of them. It has been in this case supposed, and is extremely probable, that some peculiar species of matter is produced, capable of producing fever, on being applied to the body.”

2. Effluvia from putrid animal or vegetable matters. Of this our author seems to be less fully ascertained than of the former, as he does not say that he has observed any instances of fevers arising from this cause; and he concludes by observing that “either the cause of fever, consisting of matter produced in the body of a person affected with this disease, seems probably different from that produced by putrefaction, or might be generated without any putrefaction taking place.”

3. Cold. Our author “is not disposed to allow that sudden exposure to cold occasions fever to take place, unless some symptom of the disease follows immediately. If a man had been suddenly exposed to cold, and continued in perfect health for twenty-four hours, the author would never allow that fever, or any other disease, was occasioned by it. In this case (exposure to cold) the evidence is much stronger than in that of infection; for the author (Dr. Fordyce) has seen many instances where, from exposure to cold, the commencement of the attack was instantaneous; and many are to be found in the records of medicine.”

4. Moisture. On this subject the Doctor observes, that the application of water to the body is not a cause of fever, unless the air has particles of water floating in it; in which case fever has ensued more frequently than in other cases. Water may exist in the atmosphere in three states. 1. In small drops suspended in it like dust in water. 2. In vapour. In this case the transparency of the air is not impaired, and a chemical combination, as it is called, between the air and water takes place. If the atmosphere be hot or dense, it is capable of combining chemically with a larger proportion of water. If therefore the atmosphere should in this manner be saturated with water, at any particular degree of heat or density, by diminishing either of these the vapour will be condensed, and the water reduced to the former state of suspension in small particles. 3. Water, heated to the boiling point, emits a steam, which combines chemically with the atmosphere, till the latter be saturated, after which it assumes the form of small particles; and this last is the only state which has been found to produce fever.

Moisture will also produce fever when applied to the body by wearing wet clothes. Those which imbibe or part with heat most slowly, are least apt to produce fevers on being heated. The warmer the atmosphere, the more liable people are to fevers from moisture.

It has been observed, that moisture from marshes, stagnating canals, or where the water runs very slowly, is more apt to produce fevers than what proceeds from the sea, lakes or rapid rivers. “This (says the Doctor) has given occasion to suppose that some other vapours proceed from such marshes beside water, and produce the disease. It certainly often happens, that a considerable degree of putrefaction takes place in marshy grounds, and more especially in warm climates; but it is by no means to be concluded that moisture in the atmosphere always produces fever in consequence of putrefaction. Putrefaction can only take place in vegetable or animal substances. If water therefore, not impregnated with either, should be in such a situation as to produce moisture in the atmosphere, no putrefaction can take place; therefore, if fevers ensue, they are certainly in consequence of moisture, not putrefaction. Many instances of this may be brought, as in the war which took place in Flanders, between the tenth and eleventh year of the present century, an army encamped upon sandy ground, in which water was found in digging less than a foot deep, and occasioned a great moisture in the air, which produced in a few days numbers of fevers, although the army was perfectly healthy before, and no more fevers were produced on shifting their ground. There are a vast many other instances of the same thing having taken place. Besides, fever has often arisen immediately in persons sitting in rooms, the floors of which had been just moistened with pure water.”

5. Certain kinds of food. On this Dr. Fordyce observes, that, though food of difficult digestion undoubtedly produces a number of diseases, he has never seen it productive of fever excepting once. Dr. Girtanner relates, that the emperor of Germany, having forced a number of his subjects to serve as soldiers, and sent them into an unwholsome part of Walachia, where he fed them with a kind of paste made of bread and water instead of meat, many of them died of the scurvy. The Doctor, however, does not ascribe this to any positive cause, but to three negatives, viz. the abstraction of the stimulus of nutriment, by feeding on the paste just mentioned; of the stimulus of oxygen in the corrupted atmosphere of Walachia; and lastly of the nervous stimulus, the most powerful of all; the greatest part being engaged by force against their will. This corroborates what Dr. Fordyce has said, that bad food is very seldom the cause of fever; for among so many, who used the imperial paste just mentioned, some would certainly have been affected by fevers, had it been capable of producing them; but, as it did not, it is most evident that the deficiency of stimuli is not the cause of fever.

6. Passions of the mind. These are looked upon by Dr. Fordyce to be among the less frequent causes of fever, though it is certain that they have been productive of multitudes of diseases, and even of sudden deaths; and Dr. Falconer, in his Prize Dissertation, ascribes to the passions very considerable effects in fevers, and even in the plague itself. “Contagious fevers (says he) afford strong instances of the influence of mental affections, both as prophylactics and remedies. The plague is a remarkable example, and the same reasoning extends to other disorders of a febrile, contagious nature. Fear, it is well observed by Dr. Cullen, by weakening the body, and thereby increasing its irritability, is one of the causes which, concurring with contagion, render it more certainly active, which he ascribes to its weakening effect on the body, by which its irritability is increased. Against this therefore he directs the mind to be particularly fortified, which is best done by giving people a favourable idea of the power of preservative means, and by destroying the opinion of the incurable nature of the disorder, by occupying the mind with business or labour, and by avoiding all objects of fear, as funerals, passing-bells, and any notice of the death of particular friends. Even charms might be used with good effect, could we promote a strong prepossession of their efficacy, either by the confidence they inspire, or by their engrossing the attention of the mind. It is no less certain, that a studious regard to promote hope and confidence in recovery, is equally necessary for the cure as for the prevention of such disorders. We know that contagious fevers have a peculiar tendency to diminish the energy of the brain, and of course to debilitate the whole system; and that this is especially the case with the plague, which produces the most considerable effects in weakening the nervous[82] system or moving powers, and in disposing the fluids to a general putrescency; and Dr. Cullen is of opinion that to these circumstances, as the proximate causes of the plague, regard should chiefly be had, both for the prevention and cure of this disorder. It must therefore be highly necessary, during the course of this disease, to attend to the support of the spirits, as on these the vital principles greatly depend; and they can by no means be so effectually kept up as by inspiring a confidence of recovery.”

Dr. Zimmerman presents us with a great number of examples of the influence of the passions in producing diseases, or death itself; some of the most remarkable of which follow. “All the passions (says he) when carried to excess, bring on very formidable diseases. Sometimes they occasion death, or bring us at least into imminent danger. The most reputable physicians agree in opinion that terror may occasion apoplexy, and death; and indeed they consider apoplexy as the most common effect of violent passion. Without being carried to excess, a passion will sometimes occasion a difficulty of breathing, together with a sense of stricture in the breast, and an hesitation to speak; the tongue remaining as it were immoveably fixed on the palate. Hysterical and hypocondriacal affections are sometimes the effects of grief in the most healthy people. Joy is much more dangerous to life than sudden grief. Sophocles died through joy at being crowned on account of a tragedy he had composed in his old age. The famous Fouquet died on being told that Louis XIV had restored him to liberty. The niece of the celebrated Leibnitz, not suspecting that a philosopher would hoard up treasure, died suddenly on finding under her uncle’s bed a box containing sixty thousand ducats. Violent anger has sometimes produced hæmorrhages and subcutaneous extravasations; or, some vessel of the brain being ruptured by these transports, a fatal apoplexy has taken place. There have been instances of excessive anger being succeeded by epilepsy, colic, or a violent degree of fever. Sometimes it has occasioned an increased flow of bile. In some this produces vomiting; in others it goes off downwards, and causes diarrhœa; or being retained, from a stricture of the gall-ducts, will perhaps be absorbed, and occasion jaundice. In cases where anger has been succeeded by extreme grief, obstructions have taken place in the liver. The effects of terror are similar to those of anger, but in general more violent. Sometimes excessive terror seems to give to men a preternatural strength, as is the case with madmen and drowning persons. In some cases it has not only excited immediate convulsions, but caused them to return periodically. Fear has been said to make the hair stand upright, and to contract the pores from which the hairs issue in the same manner as cold does. There are instances in authors even of the colour of the hair being changed by excessive fright. Philip V died suddenly on being told that the Spaniards had been defeated, and, on opening him, his heart was found ruptured. Timid people are more liable than others to fall sick. A firmness of mind is one of the best preservations against contagion. Willis has very well observed, that they who fear the small-pox the most are generally the first to be attacked with it. Cheyne assures us that fear is extremely prejudicial in all epidemical diseases. Dr. Rogers remarks, that fear constantly increases the ravages of a contagious disease. Rivinus attributed the propagation of the plague at Leipsic wholly to fear. The French physicians, who wrote on the plague at Marseilles, went so far as to deny its being contagious, and ascribed its propagation chiefly to fear.”

As for the cause of the plague itself, Dr. Fordyce supposes it to be produced by an infection of a particular kind. That which takes place in Syria and Egypt, he says, has only been clearly described by Dr. Russel; and it cannot be gathered from the accounts whether this may be originally produced without having been propagated as the first class of infections above mentioned are. “That disease (says he) called the plague, which ravaged this country (England) on considering the histories of the disease, seems to have been a fever,[83] produced by infections of the first class which have been enumerated.” Dr. Moore has given an account of the origin of a plague, which, if it could be depended upon, would decide the question concerning the origin of this dreadful distemper without previous infection. This passage is extracted from the History of the Royal Medical Society for the years 1777 and 1778. “Dr. Mitchell, physician to the hospital at Smyrna, appears, according to a memoir of which he is the author, sent by M. le Baron de Tott to the Medical Society to believe in the spontaneity of the plague (or that it arises of itself without any predisposing cause in the body) for proof of which he cites the following circumstance: A solitary shepherd, having no communication with any body, fell sick while he was tending his flocks; he went into an inhabited part, where he communicated the plague with which he found that he was attacked. This circumstance would prove much, if it was certain that the shepherd had no communication with others; if it were known how long, and with what precaution, he had been secluded from company: but the proofs of these are too difficult to be established to allow of any conclusion to be drawn from the fact. We are obliged therefore to acknowledge [it to be a doubtful matter] whether it is in fact a country that is the cradle of the plague; what country this is, supposing that such an one exists; or, finally, whether it sometimes appears spontaneously, and whether the first whom it attacks becomes the focus from whence it emanates.”

Dr. Fordyce, in treating of the origin of fever, seems inclined to think that it may arise without any predisposing cause; and after having enumerated the various causes already mentioned, and fully considered them, gives it as his opinion, that “there must undoubtedly be other causes than those which give occasion to the disease, but which are at present totally unknown.” In like manner Dr. Moore, speaking of the nervous fever, sums up what may be known concerning the cause of it in the following words. “Upon the whole, we know that people of delicate, exhausted and sickly constitutions, and those whose minds are saddened by depressing passions, are greatly predisposed to this disease, the immediate seeds of which, we also know, may be generated in places where human effluvia are collected and confined. And this is the most essential part of our knowledge respecting the cause of this disease; and even this little is disturbed with uncertainty: for we sometimes meet with instances of people of robust constitutions, who are seized with the disease in all its malignity, when they are under no depressing passion, when the disease is not epidemic, to whom we cannot trace it from any place where the human effluvia could be confined in any uncommon degree, or from any person in the disease, of which perhaps there is no other person ill in the neighbourhood for several miles round; and, in short, when we cannot connect it with any of the causes supposed to be the sources of the distemper. On extraordinary occasions of this kind we have nothing for it but to suppose that, notwithstanding the apparent vigour of the patient, his body has been peculiarly predisposed to catch the infection, and that some contagion, not forcible enough to infect any other person, has by some means, unobserved, been conveyed to him; or, if so many suppositions displease, we may suppose at once that there is in some cases a source of this fever which has not been suspected. For, although the numerous observations that have been made give us the strongest reason to think that human effluvia produce this disease, we have no right to infer that it cannot arise also from some other source.”

To the same purpose I subjoin the very respectable opinion and testimony of Dr. Patrick Russel. “In some epidemical distempers, the sudden alternations of the air have constant and manifest influence; in others, though the influence of the air must be equally admitted, it seems not to depend on sensible alteration or succession in the common properties of the atmosphere, but on some inexplicable combination, some occult, new, unknown quality. Amongst epidemics of this last kind must be reckoned the plague. . . . Should ever that state of the air, without the concurrence of which the contagion of the pestilence never spreads, or ceases to act, be discovered, and ascertained by unequivocal marks, the dread of the plague, universally prevalent, would be greatly diminished; more effectual means of preservation would be found out, and the application of them might safely be limited to certain seasons.

“Experience in Turky, where, generally, no precautions are taken in the times of pestilence, clearly evinces, that, in a certain state of the air, a communication with infected places may subsist without any material consequence. The return of the plague at Aleppo happens at irregular periods; the intervals are of considerable, but unequal, length; and in those the commerce with Egypt, Constantinople and Smyrna remains uninterrupted. In the intervals between 1744 1760, and from 1762 to 1780, the plague raged several times in the places now mentioned, without affecting Aleppo; and even in two or three years subsequent to 1762, though it was at Marash, as well as other places not far distant, with which Aleppo has continual intercourse, no instances were discovered of communicated infection: if such happened, they must have escaped my utmost vigilance; and the daily exercise of my profession led me to be very much among the natives of all ranks. At the same time I have reason to suspect that infected families from some of those places took refuge in Aleppo; and I know, with certainty, that not only some merchants of that city, who happened to be at Marash when the plague broke out there, returned to their families in the summer of 1763, but that caravans of various merchandise arrived in the course of the same summer.

“I consider it therefore as an established fact in the Levant, that commerce and intercourse with infected towns is sometimes attended with no bad consequence. The same thing may perhaps be asserted, without restriction, of all countries; but till the signs indicating a pestilential constitution be ascertained, no particular year can be declared exempt from danger. Predictions founded on planetary conjunctions have been long exploded; and signs derived from the known properties and alterations of the air, are almost equally fallacious. The seasons concomitant with plagues in England, as well as elsewhere, have been very dissimilar; and the same visible concurrence, usually deemed pestilential, has often, in the revolution of years, been observed to return, in various countries, without producing the dreaded consequences. Upon the whole, from all I have been able to collect, the pestilential constitution seems hitherto to be known only from its effects; neither its approach nor its retreat can be predicted and its nature remains wrapped up in MYSTERIOUS DARKNESS.”

Having thus seen, that, of the causes commonly assigned for epidemical diseases, not one can be accounted certain and determinate, it now remains to consider one more, and that is

Contagion. Though this has been generally accounted the same with infection, yet by some it has been reckoned otherwise; and indeed there seems to be a necessity for such a distinction; for, though we should prove, ever so clearly, that a disease once communicated to one person should from that person be communicated to another, yet the difficulty is to know from whence the first person had it. This source, if any such can be found, is what we may with the greatest propriety distinguish by the name of contagion, and is the sense in which it shall for the future be used in this treatise, the matter communicated from one person to another being always called infection. This indeed differs from what many celebrated physicians have said upon the subject; but the distinction certainly must exist. Dr. Cullen speaks rather indistinctly upon the subject. “We have supposed that miasmata are the cause of intermittents, and contagions the cause of continued fevers, strictly so named; but we cannot with propriety employ these general terms. The notion of contagion properly implies a matter arising from the body under disease, miasma, a matter arising from other substances. But, as the cause of continued fevers may arise from other substances than the human body, and may in such cases be called a miasma, and, as other miasmata also may produce contagious disorders, it will be proper to distinguish the cause of fevers by using the terms marsh, or human effluvia, rather than the general ones miasma, or contagion.”

From this it is not very easy to determine what the Doctor means when he speaks of specific contagion as the cause of the plague. Dr. Russel plainly ascribes it to human effluvia. “The plague (says he) is a contagious disease; that is, an emanation from a body diseased, passing into one which is sound, produces, in time, the same disease,” &c. There must, however, undoubtedly have been something originally distinct from the human body which gave rise at least to the first plague that was in the world; and some plagues recorded in history are said to have arisen in this way. Thus, Ammianus Marcellinus says that the plague which broke out in the Roman army in the time of Marcus Aurelius arose from a pestilential vapour confined in a golden coffer dedicated to Apollo. Upon opening this, the contagion diffused itself all around, and the infection spreading from one to another, produced an almost universal pestilence. Ammianus indeed is the only historian who relates this; another account of its origin is given, p. 14, but whether we believe the account of Ammianus or not (which indeed does not appear probable) it is sufficient to show what were the received opinions at the time. In like manner every one has heard of pestilential effluvia breaking out from the earth, from graves, &c. so that we certainly look upon this doctrine of contagion as the cause of diseases to have been pretty generally received. We are also informed by Dr. Mead, from M. Villani, who wrote the history of those times, that the great plague of 1346 began in China, where, according to the report of some Genoese sailors, it was occasioned by a great ball of fire that either burst out of the earth, or fell down from heaven. This is thought incredible by Dr. Mead, and no doubt is so, but it shows the general opinion, that the original cause or contagion which produces a plague is distinct from the infection which is afterwards communicated from one to another. In the French Encyclopedie, we have this account of the ball of fire, or fiery vapour, without any comment.

As to the opinion of pestilential vapours arising out of the earth, though we are assured that people have been suddenly killed by explosions, probably of the electrical kind, or by lightning issuing from under their feet, yet we are not furnished with any well authenticated accounts of a plague having arisen from any such cause. About 19 years ago a violent fever raged epidemically through a small district in the north of Scotland, which was said to have originated in the following manner. Some young men having heard that a certain place in their neighbourhood had, in the time of a plague been a burial ground, took into their heads to dig into it. They did so, and one of them immediately fell sick, but recovered. The father of two of the young men, exceedingly displeased at the conduct of his sons, and apprehensive of the consequences, filled up the hole they had dug in the ground, soon after which he fell sick and died, and the fever continued to rage in the neighbourhood for some time. The mother of another of the parties concerned also died, and boils broke out on various parts of the bodies of the sick. This was the account given in some of the news-papers of the time, and had the matter been thoroughly investigated and attested, would have been decisive in favour of pestilential contagion being capable of taking up its residence in the earth. As it stands at present, it can only draw our attention to what may happen in another case, should any similar one occur.[84]

With regard to epidemics occasioned by the action of electricity, we cannot indeed produce any instance; but we have one of a distemper more dreadful than even the plague itself; and that is of a person suddenly struck by an electric flash (generated either in his own body, or in the room where he was) and by this stroke reduced to a most deplorable condition, which soon ended in death. The account stands on the authority of Mr. Joseph Battaglia, surgeon at Ponte Bosio, who transmitted it to Florence, and is as follows.

“Don G. Maria Bertholi, a priest residing at mount Valere in the district of Livizzano, went to the fair of Filetto, on account of some business which he had to transact, and after spending the whole day in going about through the neighbouring country, in order to execute commissions, in the evening he walked towards Fenille, and stopped at the house of one of his brothers-in-law, who resided there. No sooner had he arrived, than he desired to be conducted to his apartment, where he put a handkerchief between his shoulders and his shirt, and, when every body retired, he began to repeat his breviary. A few minutes after, a loud noise was heard in Mr. Bertholi’s chamber; and his cries having alarmed the family, they hastened to the spot, where they found him extended on the floor, and surrounded by a faint flame, which retired to a greater distance in proportion as it was approached, and at length disappeared entirely. Having conveyed him to bed, such assistance as seemed necessary was given him. Next morning I was called, and after examining the patient carefully, I found that the teguments of the right arm were almost entirely detached from the flesh, and hanging loose, as well as the skin of the lower part of it. In the space contained between the shoulders and the thigh, the teguments were as much injured as those of the right arm. The first thing, therefore, to be done, was to take away those pieces of skin; and, perceiving that a mortification was begun in that part of the right hand which had received the greatest hurt, I scarified it without loss of time; but notwithstanding this precaution, I found it next day, as I had suspected the preceding evening, entirely sphacelous. On my third visit, all the other wounded parts appeared to be in the same condition. The patient complained of an ardent thirst, and was agitated with dreadful convulsions. He voided by stool bilious putrid matter, and was distressed by a continual vomiting, accompanied with a violent fever and delirium. At length the fourth day after a comatose sleep of two hours, he expired. During my last visit, while he was sunk in the lethargic sleep of which I have spoken, I observed with astonishment, that putrefaction had already made so great progress, that his body exhaled an insupportable smell. I saw the worms which issued from it crawling on the bed, and the nails of his fingers drop of themselves; so that I thought it needless to attempt any thing farther, while he was in this deplorable condition. Having taken care to get every possible information from the patient himself, respecting what had happened to him, he told me, that he had felt a stroke, as if somebody had given him a blow over the right arm, with a large club, and that at the same time, he had seen a spark of fire attach itself to his shirt, which in a moment was reduced to ashes, though the fire did not in the least injure the wrist-bands. The handkerchief which he had placed upon his shoulders, between his shirt and his skin, was perfectly entire, without the least appearance of burning, his drawers were untouched, but his night-cap was destroyed, though a single hair of his head was not hurt. That this flame under the form of elementary fire, burnt the skin, reduced the shirt to ashes, and entirely consumed the night-cap, without in the least touching the hair, is a fact which I affirm to be true: besides, every symptom that appeared on the body of the deceased, announced severe burning. The night was calm, and the circumambient air very pure: no bituminous smell could be perceived in the chamber, nor was there the least trace of fire or of smoke. A lamp, however, which had been full of oil, was found dry, and the wick almost in ashes. We cannot reasonably suppose this fatal accident to have been occasioned by any external cause; and I have no doubt that if Maffei were still alive he would take advantage of it to support an opinion which he entertained, that lightning is sometimes kindled in the human body and destroys it.”

Another account, to the same purpose, is given in Mr. Battaglia’s paper. “On the 21st of April, 1781, the first battalion of the brigade of Savoy set out from Tortona, in order to go to Arti, when the weather was excessively hot. On the 22d, having made rather a forced march, the soldiers suffered a great deal from the ardour of the sun, so that, at the village of Serre, where they halted, one of them, named Bocquet, a man of twenty-five years of age, whose skin being very hard and thick had not perspired, sent forth a loud cry, which seemed to announce some extraordinary commotion, and instantly fell down. Mr. Bianet, surgeon major to the regiment, found the patient in convulsions. When he was carried to the hospital the upper part of his body, to the thighs, appeared to be withered and black, and in a gangrenous state. Mr. Bianet employed scarifications, but without effect; it was impossible to make him swallow any thing; and it was found necessary to abandon him to his dismal fate. His body soon exhaled a putrid smell, and he died at the end of five hours. That his disorder might not be communicated to others, he was interred together with his clothes. Upon inquiry, after his death, it was found that this man was addicted to the constant use of spiritous liquors, and that he had even drank of them to excess upon the march.”

Other instances there are, still more terrible, of people actually taking fire and being consumed to ashes by some internal cause; but, as nobody was present either at the beginning or during the continuance of these extraordinary inflammations, nothing certain can be said about them. That such things, however, have happened, is certain, of which one of the most remarkable instances is that of Signora Corn. Zangari, an Italian lady. She retired to her chamber in the evening somewhat indisposed, and in the morning was found in the middle of the room reduced to ashes, all except her face, legs, skull and three fingers. The stockings and shoes she had on were not burnt in the least. The ashes were light, and on pressing them between the fingers vanished, leaving behind a gross, stinking moisture, with which the floor was smeared; the walls and furniture of the room being covered with a moist cineritious soot, which had not only stained the linen in the chests, but had penetrated into the closet, as well as into the room overhead, the walls of which were moistened with the same viscous humour. This lady had been accustomed to use a bath of camphorated spirit of wine when indisposed.

Dr. Zimmerman, from the 64th volume of the Philosophical Transactions, relates the case of a poor woman who perished in this miserable manner at Coventry in England in the year 1772. “She fell out of bed, and was found next morning burnt to death, though the fire in the grate had been small, and the furniture in the room had suffered but little. Except one thigh and leg, there were not the least remains of any skin, vessels or viscera; and the greater part of the bones were completely calcined, and covered with a whitish efflorescence.”

On these unfortunate people it has been observed that they were generally intemperate in the use of spiritous liquors. Of the poor woman at Coventry, whose case has been just now related, it is said, that she had been in the practice of drinking from half a pint to a quart of rum every day, and this she continued, notwithstanding her being affected with jaundice and other complaints. Mr. Wilmer, who communicated this case to the Royal Society, concludes it with these words: “That her solids and fluids were rendered inflammable by the immense quantity of spiritous liquors she had drank, and when she was set fire to she was probably soon reduced to ashes.”

On other cases of a similar nature it has been remarked, that the miserable sufferers were “for the most part advanced in years, remarkably fat, and had been much addicted to the use of spiritous liquors, either in their drink, or applied in friction to the body; whence it has been concluded that these people perished by their whole substance spontaneously taking fire, the principal seat of which had been the entrails, or the epigastric viscera; and that the exciting cause was naturally found in the phlogiston of the humours, called forth by that of the spiritous liquors combined with them.”[85] But solutions of this kind cannot by any means be admitted. We have not the smallest reason to think that either the solid or fluid parts of the bodies of hard drinkers are more inflammable than those of other people; neither is it credible that any person could live with his body in such a state. Besides, the most inflammable bodies will not begin to burn unless fire actually be applied to them, while others much less inflammable to appearance, will yet take fire spontaneously. Thus, even spiritous liquors themselves, though they flame violently when thrown into a fire, or when a burning body is applied to them, yet there is not an instance of such liquors taking fire of themselves; nay, they cannot even be set on fire by pouring them upon a red-hot iron, while, on the other hand, heaps of wet vegetables, which we should think scarce at all inflammable, do yet very frequently take fire spontaneously. The author lately quoted, however, justly observes that M. Bartholi, the unfortunate priest above mentioned was plainly struck first by electricity from without, a spark of fire attaching itself to his shirt, and a faint flame surrounding his body; so that the fire did not seem to have been generated in his body, but in the atmosphere. There are instances of people being surrounded with these luminous appearances without being hurt; particularly of a woman at Milan, whose bed was surrounded with a light of this kind. Mr. Loammi Baldwin, of this country, was also surrounded by an electric light, while raising a kite in the time of a thunder storm, and Dr. Priestley makes mention of a gentleman, who, after having worked an electric machine for a long time in a small room, perceived, on leaving it, a luminous vapour following him. But the instances most to our present purpose are some recorded in the Philosophical Transactions, of luminous vapours coming from the sea, attaching themselves to corn-stacks, and setting fire to them. One of this kind is particularly mentioned in Lowthorp’s Abridgement of the Transactions, as having taken place in Ireland, coming repeatedly from the sea, and setting fire to corn and hay, so that the people were greatly alarmed. At last they found that it might be driven off by making a great noise, and that it would avoid any sharp-pointed iron instrument. Had such a vapour attached itself to a human body, it is possible that it might have set fire to it as well as to the stack of corn or hay. Whether these accounts render the story of the Genoese sailors concerning the ball of fire occasioning the plague of 1346 more credible, we leave the reader to judge. They certainly show, however, that the electric fluid will sometimes interfere with the human body in a very terrible manner, producing, where it does not kill instantaneously, symptoms equal to those of the very worst plague, as in the case of the priest and soldier above mentioned.

Another hypothesis concerning the origin of pestilential diseases is that of swarms of little animals invisibly existing in the atmosphere; which, being taken into the body by the breath, are supposed to corrupt or otherwise vitiate the blood and other parts of the body, as we see in the plague and other epidemic disorders. This hypothesis, so generally exploded, and so apparently improbable, seems to receive some support from a discovery of an insect made by Mr. Henry Baker, F. R. S. and published in his work entitled “The Microscope made Easy.” He called it the insect with net-like arms. “It lives (says he) only in cascades, where the water runs very swift. Some of them being kept in a vial of water, most died in two days, and the rest, having spun themselves transparent cases, which were fastened either to the sides of the glass, or to pieces of grass put into it, seemed to be changed into a kind of chrysalis; but before they assumed this form, they altered their shape (in a manner he represents by a figure.) None of them lived above three days; and, though fresh water was given them two or three times a day, yet in a few hours it would stink to a degree scarce conceivable, and that too at several yards distance, though, in proportion to the water, all the included insects were not more than as one to one million, an hundred and fifty thousand. This makes it probable that it is necessary for them to live in a rapid stream, lest they should be poisoned by the effluvia issuing from their own bodies, as no doubt they were in the vial.”

From this account it is not difficult to conceive that animals, though exceedingly small, may yet emit such poisonous effluvia as will destroy much larger ones in their neighbourhood. It will by no means be incredible that, had one or two such offensive animals been thrown into a jar containing gold-fishes,[86] the whole of these beautiful inhabitants would have perished at once. Let us suppose such a thing to have actually happened; that a malicious person had put them in over night, and in the morning the proprietor of the fishes finds them all dead, and the water offensive to the last degree. He sends for a neighbouring philosopher, who, happening to be ignorant of the existence of such animals, endeavours to account for the phenomenon upon some of the received principles of philosophy. How much theory would here be wasted, and what endless disputes might ensue without even a possibility of arriving at the truth! Just so it is with epidemic diseases. The cause is invisible, and, until it becomes discoverable by our senses, it can never be known; for, as has already been observed, a cause never can be known merely by its effects, unless we have seen it, or somebody who has seen it gives us information. And this will certainly be found to hold good in every instance, even from the Supreme Cause himself to the diminutive insect just mentioned.

Lastly, I shall consider another possible source of epidemics, which has been hinted at by others. Allowing that infectious matter proceeds from the body of a diseased person, as much must issue from a single patient as is sufficient to bring the disease upon thousands, and with regard to the small-pox and some other distempers we certainly know that it is so. This infection is dissipated in the atmosphere, and intimately combined with it, so that it becomes imperceptible and harmless; but we have no reason to suppose that it is annihilated, or cannot be re-produced in its pristine state. Water, though perfectly dissolved, and to appearance deprived of existence in the air, may yet be precipitated from it, and pour down upon us in deluges. What happens in one case may happen in another. The infectious matter, dissolved in the air, may by some natural cause be precipitated from it, overshadowing whole regions, and, if it be not powerful enough to produce the epidemic of itself, may certainly predispose to it in such a degree, that the slightest additional cause will bring it on.

Something indeed of this kind would seem really to be the case, otherwise we cannot well conceive why there should be such a distinction of diseases. Thus the infection of the small-pox is the same all over the world. The variolous matter will never produce the measles in any country, nor will the typhus produce a pleurisy. The plague manifests itself to be the same distemper in all its various degrees of malignity, though even this dreadful disease is sometimes so mild that it does not confine the patient to his bed. There must therefore be some certain constitution in the nature of the cause which produces such and such diseases, as certainly as in the seed of particular vegetables, which gives to each its proper appearance and shape. The cause of the disease so modified we may call, with Dr. Cullen, its specific contagion.

Having thus treated so largely upon contagion of different kinds, it now remains to consider the objections that have been made to the doctrine altogether. It is indeed surprising that in so great a length of time, after the world hath so often and so dreadfully suffered from the violence of plagues, the simple fact, whether it be infectious or not, should not have been determined: nay, that it should still be questioned by physicians of no mean reputation whether such a thing as contagion or infection can possibly exist. Dr. Mosely in his treatise on tropical diseases treats the whole doctrine of contagion with the utmost contempt; calling it “a field for speculation, which has long amused the pedantry of the schools, and should never be entered into by practical writers.” Notwithstanding this, however, he doth enter into it, and with such bad success, that in the very first paragraph he is obliged to derive the cause of diseases from the stars! “There are some diseases we know, (says he) which follow the changes of the atmosphere; but there are others which make their revolutions, and visit the earth, at uncertain periods; for which we can trace no cause, depending on combinations, in which, perhaps, the influence of the planets may have some share.” Here we have a still wider field for speculation than even the schools have given us; for the Doctor ought to remember that the influence of a planet, producing a disease, is as truly contagion as the effluvia of a dunghill; and if we have a wide field to traverse when tracing it through the earth, we have one infinitely more extensive in pursuing it through the heavens. But we may be assured that planetary influence does not produce diseases; for, if it did, they would in all times of pestilence overspread the face of the earth, as the influence of the planets, if they have any, certainly does.

The arguments used by this author against terrestrial contagion are,

1. “It has often happened that hundreds of men in a camp have been seized with the dysentery, almost at the same time, after one shower of rain, &c. People under similar circumstances must be subject to similar diseases: and yet it often happens that dysentery begins with a few people, and spreads itself by degrees until a multitude are affected.”

This argument rather militates against himself; for, if dysentery or any other disease was occasioned by an evident general cause operating upon persons in similar circumstances, all of them ought to be taken ill at once; but Dr. Mosely owns that they frequently are not. There must, of consequence, be something less evident which determines the disease to particular persons, while the general cause operates equally upon all. This less evident cause we call contagion.

2. “It is incredible that the smelling a little human blood, that had stood some months in a phial, gave the man a dysentery mentioned by Pringle; or that the person Forestus speaks of got the plague by only putting his hand into an old trunk; or that the shaking an old feather-bed, which had lain by seven years, raised a plague at Wratislau, which destroyed five thousand persons in twelve weeks, as related by Alexander Benedictus, &c.—Such things may be true, but, when probability is shaken, reason always inclines to skepticism.”

Here our author most evidently contradicts himself; for in the beginning of the paragraph he tells us that the things related are incredible, and in the end of it, that they may be true. The argument, if it may be so called, is mere assertion. It is incredible that the smell of putrid human blood in a vial should produce the dysentery. Why should this be more incredible than that smelling to a charged vial should ensure an electric shock to the person who did so? This is entirely a question respecting a matter of fact, not of speculation. The same is the case with the rest. It is not more incredible that, if the infection of the plague was in a trunk, a man should get the plague by putting his hand in it, than that he should be burnt if he put his hand into a trunk full of hot ashes. Before the Doctor decided in such a positive manner, he ought to have proved that no infection could be contained in a trunk; but this, though the very point in question, he takes for granted, first telling us that the contrary is incredible, and then that it may be true!

3. “We observe in camps and hospitals, that those people whose dirty employments subject them in a particular manner to a depravation of their habits, seldom escape the present epidemic; and this gives rise to the vulgar expression, and very incorrect notion, of catching the disease. And we observe that others from the slightest deviation from regularity lose the power by which the body resists diseases, and they are also attacked. But these attacks are not to be attributed to infection: for those people who keep the vital and animal powers in uniform confederacy, by temperance and calmness of mind (for fear, by lowering the vital energy, subjects the body to disease) nourishing diet, proper clothing and cleanliness, and keeping a free and regular passage for all excretions, are proof against the assaults of foul and pestilential air. Such people seldom suffer even by the plague itself: while all around them perish.”

The first sentence of the above paragraph is so obscurely worded, that it is difficult to know the author’s meaning. I know not of any lawful employment so dirty that it necessarily subjects the person who practises it to a depravation of habit. The next ascribes every thing to intemperance and fear; from which, it seems, we are to infer that none but drunkards, cowards, and dirty, naked ragamuffins, are ever seized with epidemic diseases. But of this we are able to bring a direct disproof. I suppose Dr. Mosely will not say that the celebrated Prince Eugene of Savoy was either a coward or a drunkard; that he had a dirty employment, wanted proper food or clothes, or was deficient in personal cleanliness; yet, when in the marshy parts of Hungary, he was in danger of death from an epidemic dysentery, notwithstanding that he was so careful in respect of diet, that he had pure water brought him every day, probably from a considerable distance. How came he to be affected by the distemper under such circumstances, while Count Boneval, though as an inferior officer he probably enjoyed fewer advantages, remained free from it, taking only a small quantity of Peruvian bark daily? It is uncertain whether the bark did really preserve him or not; but the case of Prince Eugene plainly shows that sobriety, temperance, valour and cleanliness are not sufficient to ward off an epidemic disease, if people come in the way of infection.

4. “It should follow, if contagion were supported by infected bodies, that no person should ever escape infection (as at Oxford assizes in 1577[87]) who was within the sphere of its action; and that those who were entirely secluded from it, and free from all contiguity to infected people, or substances, as the collegers were in the town of Cambridge, when the plague was last in England, should be exempt from it.

“But, in opposition to this, Rhazes lived 120 years, an often practised in plagues. Hodges remained in town, and attended the sick, during the great plague in 1665. Kaye was in the midst of practice in the sweating sickness in 1551, without any inconveniency. Procopius informs us, that during a terrible plague at Constantinople, in 543, which almost destroyed the whole city, no physician nor other person got the plague by attending, dressing or touching the sick. Yet most of the Capuchins, the Jesuits, the Recollets, the Observantines, the Barefooted Carmelites, the Reformed Augustines, all the Grand Carmelites, the Grand Trinitarians, the Reformed Trinitarians, the Monks of Loretto, of Mercy, the Dominicans, and Grand Augustines, who kept themselves secluded in their several convents, and took every precaution to avoid the plague, while it raged at Marseilles, perished by it.

“There are no epidemical nor contagious diseases that attack every person who breathes the same air, or that is in contact with the infection, else whole regions would be depopulated. The habit must be graduated, or adapted, for the reception of a disease. In some constitutions of body the access is easy, in some difficult, in others impossible. But where the revelation of this mystery is to be found, none can tell.”

In this, which our author seems to have designed as his grand argument, it is plain that the deficiency is as great as in any of the rest. If we suppose the plague, or any other epidemic disease, to arise from some general cause, let that cause be contagion or any thing else, it ought to operate upon all who come within its sphere of action, as Dr. Mosely observes of infection. If experience shows that it does not, the argument will hold equally against a constitution of the atmosphere, putrid effluvia, heat, cold, or any thing else; and in fact the Doctor fairly gives up the point at last, by resolving the whole into an unrevealed mystery. With regard to what he says about the plague at Marseilles getting into the convents, of which he presents us with such a catalogue, it is impossible to know what precautions were used, and we are assured that in Turky it is thought necessary for the Europeans not only to guard against a communication with their own species, but some of the brute creation also. Cats particularly are dreaded so much, that a general massacre of them commences among those who use precautions, the favourites of that species must be sent to a distance, and M. Volney mentions two merchants who had shut up their houses, and yet had the plague imported by a cat. In short, considering that infection is supposed to be altogether invisible and imperceptible, it is impossible to say how it may be conveyed, or to what extent it may occasionally act when once brought into a country. Dr. Fordyce is of opinion that the distance at which infection may act depends on the disposition of the air at the time; and he observes, that a difference in this respect is observable in the odoriferous effluvia of vegetables. “If the air be loaded with moisture, they reach to a much greater distance. Vapour arising from a field of beans, for instance, or a putrid ditch, is sensible to the nostrils at a greater distance if the air is moist.” He observes indeed that this has never been verified with regard to infection; but as it is evidently the case with putrid effluvia, which very often accompany infection, we may reasonably conclude that it is the case with the latter also.

Let us next take a view of what is advanced by the authors of The Science of Life upon this subject. Mr. McLean, who puts his name to this part, informs us of his conviction “that no general disease, which affects a person more than once during life, can ever be communicated by contagion;” and he defines contagion “a specific matter, generated in a person affected with disease, and capable of communicating that particular disease, with or without contact, to another.” It would here be no improper question, by what means he comes to know that a contagious disease can affect a person only once. But even this question is unnecessary. Dr. Guthrie gives an account of a gentleman who had the courage to inoculate himself for the plague, in consequence of which he had the disease with the concomitant symptoms of buboes, &c. Here then we see the plague communicated by “a specific matter generated in a person affected” with the same disease, i. e. by contagion, according to Mr. McLean’s own definition. The dispute therefore might stop, as this fact seems to be decisive on the subject; but as he has at great length insisted upon the argument last quoted from Dr. Mosely, it seems necessary to follow him a little farther.

“If a person (says our author) be affected with any disease, it will necessarily be communicated to every other person who comes within the infectious distance, and is not at the same time labouring under some disease higher in degree.” This proceeds upon a supposition that his theory is absolutely perfect and infallible; which, however plain it may appear to himself, will not probably be admitted by others without some proof. Indeed he himself afterwards adduces some facts which decisively overthrow it. “A child (says he) here and there is exempted from small-pox, even though exposed to its contagion.” How comes this to pass? The disease, we are told, is contagious, the child is exposed to the contagion, and yet is not affected. In all such cases it would be ridiculous to suppose the subjects labouring under a disease higher in degree than the contagion could produce. In numbers of instances of this kind the children were evidently in good health, and yet would perhaps be seized at an after period when no more exposed to contagion than they had been at first.

“Small-pox, measles, and other general diseases, which occur only once during life, never disappear, until the whole of those who have been within the infectious distance, and were not at the time labouring under some disease higher in degree, have received the infection. As these diseases are very mild, children sometimes resist the power of contagion from the superior force of some other diseases, although they may be so slight as to escape common observation.”

In this paragraph we have the favourite maxim of our author repeated, twice indeed, without a single fact to support it. Instead of this we find hypothesis heaped upon hypothesis, as the giants are said to have heaped mountains upon one another in order to get up to heaven. He first supposes that the infection of the small-pox seizes on the whole of those on whom it falls. The exceptions to this maxim he explains by another supposition, viz. that the contagion of the small-pox is counteracted by another disease. The second hypothesis is supported by a third, and that a very extraordinary one, that the small-pox (a disease which has destroyed innumerable multitudes) is very mild; and this third by a fourth, that the diseases which counteracted the contagion were so slight as to escape common observation. It was incumbent on Mr. McLean to have pointed out some of those diseases, and to have informed us how they came to counteract this contagion. But it is needless to argue with one who writes so extravagantly. Far from the mode of reasoning followed by Dr. Fordyce, who decided from the majority of facts, our author determines every thing by his own preconceived opinions. “That the power which occasioned disease at the Oxford assizes (says he) was not contagious matter, is proved by its producing diarrhœa in some, while it produced fevers in others.” But, if it was not contagious matter, what kind of matter was it? Or how comes our author to know that those who were affected by the diarrhœa were not likewise affected by fever? How many fevers are attended by diarrhœa, or how many cease when diarrhœa comes on! It would have been equally conclusive to say that the matter was not contagious, because some died and some recovered.

I shall only take notice of one assertion more, it being both tedious and unnecessary to follow him through the whole. “From every record of epidemic and pestilential diseases, it would appear, that they have their stated periods of recurrence; that these periods are such months as are most remarkable for vicissitudes of the atmosphere; that they become general only in those years in which these vicissitudes are extreme; that they do not occur in seasons when the heats or colds, however intense, are equable; nor in years when the state of the atmosphere is tempered throughout; and that they uniformly cease with the establishment of an equable state of the atmosphere, whether the weather be cold or hot. . . . In Aleppo, according to Dr. Russel, the Europeans regularly shut themselves up in their houses every year, at some period between April and July; and the rich natives begin to adopt the same plan, &c. . . . From this fact it appears, that the plague occurs at Aleppo, in a state more or less mild, almost annually, and that it commences and ceases at certain known periods. But it has been remarked that, in its most severe state, this disease recurs only at periods of ten years, or thereabouts: a regularity which cannot, upon any known principle, be attributed to a power of such casual application as contagious matter.”

In the beginning of this paragraph our author makes a bold appeal to every record of epidemic and pestilential disorders; but here we may ask, Has he consulted every record of these disorders? That he has not, we may readily believe; but even those which are hinted at seem either to have been very inaccurately consulted, or wilfully misrepresented. To evince this I subjoin the following abstract of what Dr. Alexander Russel says of the plague in general, with the annotations of his brother, Dr. Patrick, taken from Russel’s Natural History of Aleppo.

The inhabitants of Aleppo suppose that the plague visits them once in ten years, and that it is always imported; and the most severe plagues are thought by some to come from Damascus, while others contend that they come from the northward. Dr. Alexander Russel thinks this popular opinion of the return of the plague not altogether unfounded; and he thinks it also probable that it never invades Aleppo without having previously attacked either Damascus or Khillis, Aintab, Marash or Uufa. He thinks that its appearance always is in one of the maritime towns of Syria; if in Sidon, Byroot or Tripoli, Damascus is commonly the channel by which it reaches Aleppo; but, if it shows itself first at Scanderoon or Byass, its approach is by the way of Khillis or Aintab.

On this Dr. Patrick Russel observes, that the account of Aleppo being visited only once in ten or twelve years is confirmed by a letter from an English gentleman, in 1719, who had resided there for 30 years. The dates of the plagues which Dr. Patrick had procured were, 1719, 1729 and 1733. Another began in 1742, and terminated in 1744; from which time there was no return till 1757 or 1758, when it continued at Aleppo till 1762, and did not entirely quit the country till 1764. The plague of 1719 was said to come from the northward, but this appeared to want confirmation; but all accounts agree that it raged at Tripoli, Sidon, &c. two months before it appeared in Aleppo. Egypt was ravaged by the plague in 1728, as was also Byass and the neighbouring parts in the same summer; and next year it appeared at Aleppo. In 1732 it raged at Sidon, Tripoli and Damascus; next year it seized Aleppo.

Dr. Alexander goes on to inform us, that the disease never spreads much in winter. It advances with the spring, comes to its height in June, declines in July, and terminates in August. “None (he says) are ever seized with in September and October, not even in the plague of 1742, which returned three years successively;” but Dr. Patrick says that this was not confirmed by his experience in 1760, though he owns that the distemper declines remarkably at that period; and the natives are greatly inclined to have it believed that the distemper has totally ceased, and to deceive the Europeans in this respect. The times at which the Europeans shut up and come out of their confinement show only the increase or decrease of the disease, but not its beginning or ending. The plague of 1719 made terrible havoc. Europeans then shut up about the middle of March, and kept confined till the middle of July. In 1729 they did not shut up till the middle of May, and were not confined above a month, the number of sick being small. In 1733 they were confined from the middle of March to the middle of July, but the distemper was less violent than in 1719. In 1742 the time of confinement much as in 1729. In 1743 shut up April 11, and opened the middle of July. The plague violent, but less so than in 1733. In 1744 few shut up, the number of sick being inconsiderable. In 1760 they shut up on the 30th of June, and continued about a month. In 1761 shut up May 28, rode out Aug. 1, and opened completely the 10th of that month. In 1762 they were confined from the last week in May to the first of August. From 1762 to 1787, a larger period than usual, the city was free from the plague. In 1787 it broke out among the Jews in the month of April, increased in May, raged violently in June, and terminated in July.