Buffon's Natural History, Volume 03 (of 10) / Containing a Theory of the Earth, a General History of Man, of the Brute Creation, and of Vegetables, Minerals, &c. &c.

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Barr's Buffon.

Buffon's Natural History.

CONTAINING

A THEORY OF THE EARTH,

A GENERAL

HISTORY OF MAN,

OF THE BRUTE CREATION, AND OF
VEGETABLES, MINERALS,
&c. &c.

FROM THE FRENCH.

WITH NOTES BY THE TRANSLATOR.

IN TEN VOLUMES.

VOL. III.

PRINTED FOR THE PROPRIETOR,

SOLD AND BY H. D. SYMONDS, PATERNOSTER-ROW.

1807.

T. Gillet, Printer, Wild-Court

CONTENTS
OF
THE THIRD VOLUME.

History of Man.

Directions for placing the Plates.

[BUFFON'S]
NATURAL HISTORY.

[HISTORY OF ANIMALS.]

Aristotle admits, with Plato, of final and efficient causes. These efficient causes are sensitive and vegetative souls, that give form to matter which, of itself, is only a capacity of receiving forms; and as in generation the female gives the most abundant matter, and it being against his system of final causes to admit that what one could effect should be performed by many, he concludes, that the female alone contains the necessary matter to generation; and, as another of his principles was, that matter itself is unformed, and that form is a distinct being from matter, he affirmed that the male furnished the form, and, consequently, nothing belonging to matter.

Descartes, on the contrary, who admitted but a few mechanical principles in his philosophy, endeavoured to explain the formation of the fœtus by them, and thought it in his power to comprehend, and make others understand, how an organized and living being could be made by the laws of motion alone. His admitted principles differed from those used by Aristotle; but both, instead of examining the thing itself, without prepossession and prejudice, have only considered it in the point of view relative to their systems of philosophy, which could not be attended with a successful application to the nature of generation, because it depends, as we have shewn, on quite different principles. Descartes differs still more from Aristotle, by admitting of the mixture of the seminal liquor of the two sexes; he thinks both furnish something material for generation, and that the fermentation occasioned by the mixture of these two seminal liquors causes the formation of the fœtus.

Hippocrates, who lived under Perdicas, a considerable time before Aristotle, established an opinion, which was adopted by Galen, and a great number of physicians who followed him; his opinion was, that the male and female had each a prolific fluid, and supposed, besides, that there were two seminal fluids in each sex, the one strong and active, the other weak and inactive.[A] That a mixture of the two strongest fluids produce a male child, and of the two weakest a female; so that, according to him, they each contain a male and a female seed. He supports this hypothesis by the following circumstance; that many women, who produce only girls by their first husbands, have produced boys by a second; and that men, who have had only girls by their first wives, have had boys by others. It appears to me, that if even this circumstance could be well established, it would not be necessary to give to the male and female two kinds of seminal liquor for an explanation; because it may easily be conceived, that women, who have brought forth only girls by their first husbands, and produced boys with other men, were only those who furnished more particles proper for generation with their first husband than with the second; or that the second husband furnished more particles proper for generation with the second wife than with the first; for when, in the instant of conception, the organic molecules of the male are more abundant than those of the female, the result will be a male, and when those of the female abounds a female will be produced; nor is it in the least surprising that a man should have a disadvantage in this respect with some women, while he will have a superiority over others.

[A] See Hippocrates, lib. de Genitura, page 129, & lib. de diæta, page 198, Lugd. Bat. 1665, vol. I.

This great physician supposes, that the seed of the male is a secretion of the strongest and most essential parts of all that is humid in the human body; and he thus explains how this secretion is made: "Venæ & nervi, he says, ab omni corpore in pudendum vergunt, quibus dum aliquantulum teruntur & calescunt ac implentur, velut pruritus incidit, ex hoc toti corpori voluptas ac caliditas accidit; quum vero pudendum teritur & homo movetur, humidum in corpore calescit ac diffunditur, & a motu conquassatur ac spumescit, quemadmodum alii humores omnes conquassati spumescunt.

"Sic autem in homine ab humido spumescente id quod robustissimum est ac pinguissimum secernitur, & ad medullam spinalem venit; tendunt enim in hanc ex omni corpore viæ, & diffundunt ex cerebro in lumbus ac in totum corpus & in medullum; & ex ipsa medull proacedunt viæ, ut & ad ipsum humidum perferatur & ex ipsa secedat; postquam autem ad hanc medullam genitura pervenerit, procedit ad renes, hac enim via tendit per venas, & si renes fuerint exulcerati, aliquando etiam sanguis defertur: a renibus autem transit per medois testes in pudendum, proce dit autem non qua urina, erum alia ipsi via est illi contigua, &c."[B]

[B] See Fæsius's Translation, vol. I. page 129.

Anatomists will no doubt discover that Hippocrates is not correct in tracing the road of the seminal liquor; but that does not affect his opinion, that the semen comes from every part of the body, and particularly the head, because, he says, those whose veins have been cut which lie near the ears only bring forth a weak, and very often an unfertile semen. The female has also a seminal fluid, which she emits, sometimes within the matrix, and sometimes without, when the internal orifice is more open than it should. The semen of the male enters into the matrix, where it mixes with that of the female; and as each has two kinds of fluid, the one strong and the other weak, if both furnish their strong, a male will be the result, and if their weak, a female; and if in the mixture there are more particles of the male liquor than the female, then the infant will have a greater resemblance to the father than to the mother, and so on the contrary. It might here be asked Hippocrates what would happen when the one furnished its weak semen and the other its strong? I cannot conceive what answer he could make, and that alone is sufficient to cause his opinion of two seeds in each sex to be rejected.

In this manner then, according to him, the formation of the fœtus is made: the seminal fluids first mix in the matrix, where they gradually thicken by the heat of the body of the mother; the mixture receives and attracts the spirit of the heat, and when too warm part of the heat flies out, and the respiration of the mother sends a colder spirit in; thus alternatively a cold and a hot spirit enter the mixture, which give life, and cause a pellicle to grow on the surface, which takes a round form, because the spirits, acting as a centre, extend it equally on all sides. "I have seen, says this great man, a fœtus of six days old; it was a ball of liquor surrounded with a pellicle; the liquor was reddish, and the pellicle was spread over with vessels, some red and others white, in the midst of which was a small eminence, which I thought to be the umbilical vessels, by which the fœtus receives nourishment and the spirit of respiration from the mother. By degrees another pellicle is formed, which surrounds the first; the menstrual blood, being suppressed, abundantly supplies it with nutriment, and which coagulates by degrees, and becomes flesh; this flesh articulates itself in proportion as it grows, and receives its form from the spirit; each part proceeds to take its proper place; the solid particles go to their respective situations and the fluid to theirs: each matter seeks for that which is most like itself, and the fœtus is at length entirely formed by these causes and these means."

This system is less obscure and more reasonable than that of Aristotle, because Hippocrates endeavours to explain every matter by particular reasons: he borrows from the philosophy of his times but one single principle, which is, that heat and cold produce spirits, and that those spirits have the power of ordering and arranging matter. He has viewed generation more like a physician than a philosopher, while Aristotle has explained it more like a metaphysician than a naturalist; which makes the defects of Hippocrates's system particular and less apparent, while those of Aristotle's are general and evident.

These two great men have each had their followers; almost all the scholastic philosophers, by adopting Aristotle's philosophy, received his system of generation, while almost every physician followed the opinion of Hippocrates; and seventeen or eighteen centuries passed without any thing new being said on the subject. At last, at the restoration of literature, some anatomists turned their eyes on generation, and Fabricius Aquapendente was the first who made experiments and observations on the impregnation and growth of the eggs of a fowl. The following is the substance of his observations.

He distinguished two parts in the matrix of a hen, the one superior and the other inferior. The superior he calls the Ovarium, which is properly no other than a cluster of small yellow eggs of a round form, varying in size from the bigness of a mustard-seed to that of a large nut or medlar. These small eggs are fastened together by one common pellicle, and form a body which nearly resembles a bunch of grapes. The smallest of these eggs are white, and they take another colour in proportion as they increase.

Having examined these eggs immediately after the communication of the cock, he did not perceive any remarkable difference, nor any of the male semen in any one of these eggs; he therefore supposed that every egg, and the ovarium itself, became fruitful by a subtle spirit, which came from the semen of the male; and he says, that in order to secure this fecundating spirit, nature has placed at the external orifice of the vagina of birds a kind of net-work or membrane, which permits, like a valve, the entrance of this seminal spirit, but at the same time prevents it from re-issuing or evaporating.

When the egg is loosened from the common pellicle, it descends by degrees through a winding passage into the internal part of the matrix. This passage is filled with a liquor nearly similar to the white of an egg; it is also in this part that the eggs begin to be surrounded with this white liquor, with the membrane which occasions it, the two ligaments (chalazæ) which passes over the white, and connects it with the yolk and shell, which are formed in a very short time before they are laid. These ligaments, according to Fabricius, is the part of the egg fecundated by the seminal spirit of the male; and it is here where the fœtus first begins to form. The egg is not only the true matrix, that is to say, the place of the formation of the chick, but it is from the egg all generation depends. The egg produces it as the agent: it supplies both the matter and the organs; the ligaments are the substance of formation; the white and the yolk are the nutriment, and the seminal spirit of the male is the efficient cause. This spirit communicates to the ligaments at first an alterative faculty, afterwards a formative, and lastly the power of augmentation, &c.

These observations of Fabricius have not given us a very clear explication of generation. Nearly at the same time as this anatomist was employed in these researches, towards the middle of the sixteenth century, the famous Aldrovandus[C] also made observations on eggs; but as Harvey judiciously observes, he followed Aristotle much closer than experiment. The descriptions he gives of the chicken in the egg are not exact. Volcher Coiter, one of his scholars, succeeded much better in his enquiries; and Parisanus, a physician of Venice, having also laboured on this subject, they have each given a description of the chicken in the egg, which Harvey prefers to any other.

[C] See his Ornithology.

This famous anatomist, to whom we are indebted for the discovery of the circulation of the blood, has composed a very extensive treatise on generation; he lived towards the middle of the last century, and was physician to Charles I. of England. As he was obliged to follow this unfortunate prince in his misfortunes, he lost what he had written on the generation of insects among other papers, and he composed what he has left us on the generation of birds and quadrupeds from his memory. I shall concisely relate his observations, his experiments, and his system.

Harvey asserts that man and every animal proceed from an egg; that the first produce of conception in viviparous animals is a kind of an egg, and that the only difference between viviparous and oviparous is, that the fœtus of the first take their origin, acquire their growth, and arrive at their entire expansion in the matrix; whereas the fœtus of oviparous animals begins to exist in the body of the mother, where they are merely as eggs, and it is only after they have quitted the body of the mother that they really become fœtuses; and we must remark, says he, that in oviparous animals, some hold their eggs within themselves till they are perfect, as birds, serpents and oviparous quadrupeds; others lay their eggs before they are perfect, as fish, crustaceous, and testaceous animals. The eggs which these animals deposit are only the rudiments of real eggs, they afterwards acquire bulk and membranes, and attract nourishment from the matter which surrounds them. It is the same, adds he, with insects, for example, and caterpillars, which only seem imperfect eggs, which seek their nutriment, and at the end of a certain time arrive to the state of chrysalis, which is a perfect egg. There is another difference in oviparous animals: for fowls and other birds have eggs of different sizes, whereas fish, frogs, &c. lay them before they are perfect, have them all of the same size; he indeed observes, that in pigeons, who only lay two eggs, all the small eggs which remain in the ovarium are of the same size, and it is only the foremost two which are bigger than the rest. It is the same, he says, in cartilaginous fish, as in the thornback, who have only two eggs which increase and come to maturity, while those which remain in the ovarium are, like those in fowls, of different sizes.

He afterwards makes us an anatomical exposition of the parts necessary to generation, and observes, that in all birds the situation of the anus and vulra are contrary to the situation of those parts in other animals; the anus being placed before and the vulra behind;[D] and with respect to the cock, and all small birds, that they generate by external friction, having in fact no intermission nor real copulation; with male ducks, geese, and ostriches, it is evidently otherwise.

[D] Most of these articles are taken from Aristotle.

Hens produce eggs without the cock, but in a very small number, and these eggs, although perfect, are unfruitful: he does not agree with the opinion of country people, that two or three days cohabitation with the cock is sufficient to impregnate all the eggs a hen will lay within the year, but admits that he separated a hen from a cock for the space of twenty days, and that all the eggs she laid during that space were fecundated. While the egg is fastened to the ovarium, it derives its nutriment from the vessel of the common pellicle. But as soon as it is loosened from it, it derives the white liquor which fills the passages in which it descends, and the whole, even to the shell, is formed by this mode.

The two ligaments (chalazæ) which Aquapendente looks on as the shoot produced by the seed of the male, are found in the infecund eggs which the hen produces without the communication with the cock, as in those which are impregnated: and Harvey very judiciously remarks, that those parts do not proceed from the male, and are not those which are fecundated; the fecundated part of an egg is a very small white circle which is on the membrane that covers the yolk, and forms there a small spot, like a cicatrice, about the size of a lentil. Harvey also remarks, that this little cicatrice is found in every fecund or infecund egg, and that those who think it is produced by the seed of the male are deceived. It is of the same size and form in fresh eggs, as in those which have been kept a long time; but when we would hatch them, and when the egg receives a sufficient degree of heat, either by the hen, or artificially, we presently see this small spot increase and dilate nearly like the sight of the eye. This is the first change, and is visible at the end of a few hours incubation.

When the egg has undergone a proper warmth for twenty-four hours, the yolk, which was before in the centre of the shell, approaches nearer to the cavity at the broad end; this cavity is increased by the evaporation of the watery part of the white, and the grosser part sinks to the small end. The cicatrice, or speck, on the membrane of the yolk, rises with it to the broad end, and seems to adhere to the membrane there: this speck is then about the bigness of a small pea, in the middle of it a white speck is discernible, and many circles, of which this point seems to form the centre.

At the end of the second day these circles are larger and more visible; the streak also appears divided by these circles into two, and sometimes three parts of different colours; a small protuberance also appears on the external part, and nearly resembles a small eye, in the pupil of which there is a point, or little cataract; between these circles a clear liquor is contained by a very delicate membrane, and the speck now appears more to be placed in the white than on the membrane of the yolk. On the third day the transparent liquor is considerably increased, as is also the small membrane which surrounds it. The fourth day, a small streak of purple-coloured blood is observed at the circumference of the speck or ball, at a little distance from the centre of which a point may be seen of a blood colour, and which beats like a heart. It appears like a small spark at each diastole, and disappears at each systole; from this animated speck issue two small blood vessels, which these small vessels throw out as branches into this liquor, all of which come from the same point, nearly in like manner as the roots of a tree shoot from the trunk.

Towards the end of the fourth day, or at the beginning of the fifth, the animated speck is so much increased as to appear like a small bladder filled with blood, and by its contractions and dilations is alternatively filled and emptied. In the same day this vessel very distinctly appears to divide into two parts, each of which alternatively impel and dilute the blood in the same manner. Around the shortest sanguinary vessel which we have spoken of a kind of cloud is seen, which, although transparent, renders the sight of this vessel more obscure; this cloud constantly grows thicker and more attached to the root of the blood vessel, and appears like a small globe: this small globe lengthens and divides into three parts, one of which is globular, and larger than the other two; the head and eyes now begin to appear, and at the end of the fifth day, the place for the vertebra is seen in the remainder part of this globe.

The sixth day the head is seen more clearly, the outlines of the eyes now appear, the wings and thighs lengthen, and the liver, lungs, and beak, are distinctly observed; the fœtus now begins to move and extend its head, although it has as yet only the internal viscera; for the thorax, abdomen, and all the external coverings of the fore part, of the body are wanting. At the end of this day, or at the beginning of the seventh, the toes appear, the chick opens and moves its beak, and the anterior parts of the body begin to cover the viscera; on the seventh day the chicken is entirely formed, and from this time until it comes out of the egg, nothing happens but only an expansion of those parts it acquired within these first seven days: at the fourteenth or fifteenth day the feathers appear, and at the twenty-first it breaks the shell with its beak, and procures its enlargement.

These observations of Harvey appear to have been made with the greatest exactness; nevertheless we shall point out how imperfect they are, and that he has fallen himself into the error he reproaches others with, making experiments to support his favourite hypothesis, that the heart was the animated speck which first appeared; but before we proceed on this matter, it is but just to give an account of his other observations, and of his system.

It is well known that Harvey made many experiments on hinds and does. They receive the male towards the middle of September: a few days after copulation the horns of the matrix become thicker, and at the same time more lax. In each of the cavities five carunculas appear. Towards the 26th or 28th of the above month the matrix thickens still more, and the five carunculas are swelled nearly to the shape and size of a nurse's nipple; by opening them, an infinity of small white specks are found. Harvey pretends to have remarked, that there was neither then, nor immediately after copulation, any alteration or change in the ovarium, and that he has never been able to find a single drop of the seed of the male in the matrix, although he has made many researches for that purpose.

Towards the end of October, or beginning of November, when the females separate from the males, the thickness of the horns begins to diminish, the internal surfaces of their cavities are swelled, and appear fastened together; the carunculas remain, and the whole, which resembles the substance of the brain, is so soft that it cannot be touched. Towards the 13th or 14th of November, Harvey says, that he perceived filaments, like the threads of a spider's web, which traversed the cavities of the horns and the matrix itself: these filaments shoot out from the superior angle of the matrix, and by their multiplication form a kind of membrane, or empty tunic; a day or two after this tunic is filled with a white, aqueous and glutinous matter, which adheres to the matrix by a kind of mucilage; and in the third month this tunic, or pouch, contains an embryo about the breadth of two fingers long, and another internal pouch, called the amnios, containing a transparent crystalline liquor, in which the fœtus swims. The fœtus at first was but an animated speck, like that in the egg of a fowl. All the rest is performed in the same manner as that related of the chick; the only difference is in the eyes, which appears much sooner in the fowl than in the deer. The animated speck appears about the 19th or 20th of November, a day or two after which the oblong body, which contains the fœtus, is seen; in six or seven days more it is so much formed that the sex and limbs may be distinguished; but the heart and viscera are yet uncovered, and it is two days more before the thorax and the abdomen cover them, which is the last work and completion of the edifice.

From these observations upon hens and deer, Harvey concludes, that all female animals have eggs, that in these eggs a separation of a transparent crystalline liquor contained in the amnios is made, and that another external pouch, the chorion, contains the whole liquors of the egg; that the first thing which appears in the crystalline liquor is the sanguinary and animated spirit; in a word, that the formation of viviparous animals is made after the same manner as oviparous; and he explains the generation of both as follows.

Generation is the work of the matrix, in which no seed of the male ever enters; the matrix conceives by a kind of contagion, which the male liquor communicates to it, nearly as the magnet communicates its magnetic virtue to steel. This male contagion not only acts upon the matrix but over all the female body, which is wholly fecundated, although the matrix only has the faculty of conception, as the brain has the sole faculty of conceiving ideas. The ideas conceived by the brain, are like the images of the objects transmitted by the senses; and the foetus, which may be considered as the idea of the matrix, is like that which produces it. This is the reason that a child has a resemblance to its father, &c.

I shall not follow this anatomist any farther; what I have mentioned is sufficient to judge of his system; but we have some remarks to make on his observations. He has given them in a manner most likely to impose; seems to have often repeated his experiments, and to have taken every necessary precaution to avoid deception; from which it might be imagined he had seen all he writes upon, and observed them with the greatest accuracy. Nevertheless, I perceive both uncertainty and obscurity in his descriptions; his observations are related chiefly on memory; and although he often says the contrary, Aristotle appears to have been his guide more than experience; for he has only seen in eggs what Aristotle has before mentioned; and that most of his observations which may be deemed essential had been made before him, we shall be perfectly convinced if we pay a little attention to what follows:

Aristotle knew that the ligaments (Chalazæ) were of no service to the generation of the chicken. "Quæ ad principium lutei grandines hærent, nil conferunt ad generationem, ut quidam suspicantur."[E] Parisanus, Volcher, Coiter, Aquapendente, and others, remarked the cicatrice as well as Harvey: Aquapendente supposed it of no use; but Parisanus pretended that it was formed by the male semen, or at least that the white speck in the middle of the cicatrice was the seed of the male which would produce the chicken. "Est-que, says he, illud galli semen alba & tenuissima tunica abductum, quod substat duabus communibus toti ovo membranis, &c." Therefore the only discovery which properly belongs to Harvey is, his having observed that this cicatrice is found in infecund as well as fecundated eggs; for others had observed, like him, the dilation of the circles, and the growth of the white speck; and it appears that Parisanus had seen it much better; this is all which he remarks in the two first days of incubation; and what he says of the third day, is only a repetition of Aristotle's words. [F]"Per id tempus ascendit jam vetellus ad superiorem partem ovi acutiorem, ubi & principium ovi est & fœtus excluditur; corque ipsum apparet, in albumine sanguinei puncti, quod punctum salit & movet sese instar quasi animatum; ab eo meatus venarum specie duo, sanguinei pleni, flexuosi, qui, crescente fœtu, feruntur in utramque tunicam ambientem, ac membrana sanguineas fibras habens eo tempore albumen continet sub meatibus illis venarum similibus; ac paulo post discernitur corpus pufillum initio, ommino & candidum, capite conspicuo, atque in eo oculis maxime turgidis qui diu sic permanent, sero enim parvi fiunt ac considunt. In parte autem corporis inferiore, nullum extat membrum per initia, quod respondeat superioribus. Meatus autum illi qui a corde prodeunt, alter ad circumdantem, membranam tendit, alter ad luteum, officio umbilici."

[E] Hist. Anim. lib. vi. cap. 2.

[F] Hist. Anim. lib. vi. cap. 4.

Harvey attacks Aristotle for saying that the yolk ascends towards the small end of the egg, and concludes, that he had not seen any thing himself, but had apparently received his information from some good observer of Nature. Harvey was wrong in thus reproaching Aristotle, and in asserting that the yolk always ascends towards the broad end of the egg, for that depends on the position of the egg during the time of incubation, for the yolk always ascends to the uppermost part, as being lighter than the white, whether it be to the broad or the small end. William Langley, a physician at Dordrecht, who made observations on the hatching of eggs, in 1655, twenty years before Harvey, was the first who made this remark.[G]

[G] See Wm. Langley Observ. edæ a justo Schradero, Amst. 1674.

But to return to the passage we have quoted. By that we see that the crystalline liquor, the animated speck, the two circles, the two blood vessels, &c. are described by Aristotle precisely as Harvey had seen them. This anatomist also pretends that the animated speck is the heart, that this heart is formed the first, and that the viscera and other parts are joined afterwards. All this has been spoken of by Aristotle, and seen by Harvey, and nevertheless it is not conformable to truth. To be assured of this we need only repeat the same experiments on eggs, or only read with attention those of Malpighius,[H] which were made about 40 years after those of Harvey.

[H] Malpighii pullus in ovo.

This excellent observer of Nature examined, with attention, the cicatrice, which is the essential part of the egg; he found it was large in all impregnated eggs, and small in those which were not impregnated; and he discovered in eggs which had never been sat upon, that the white speck, spoken of by Harvey as the first which becomes animated, is a small pouch or ball, which swims in a liquor inclosed by the first circle, and in the middle of this ball he observed the embryo. The membrane of this small pouch, which is the amnios, being very thin and transparent, permitted him easily to see the fœtus it surrounded. Malpighius, with reason, concludes, from this first observation, that the fœtus exists in the egg before incubation, and that its first outlines are then very strong. It is not necessary to point out how opposite this experiment is to the opinion of Harvey, for he saw nothing of a form for the two first days of incubation, and it was the third day before the sign of the fœtus appears, which is the animated speck: whereas according to Malpighius, the outlines of the fœtus exist in the egg before incubation has commenced.

After being assured of this important matter, Malpighius examined, with like attention, the cicatrice of unimpregnated eggs, which, as we have observed, is smaller than those which have been impregnated; it has often irregular circumscriptions, and sometimes differs in different eggs. Near its centre, instead of the ball that encloses the fœtus, there is a globular mole, which does not contain any thing organized, and which being opened does not present any thing formed or arranged, but only some appendages filled with a thick but transparent fluid; and this unshapen mass is surrounded with many concentric circles.

After six hours incubation the cicatrice is considerably dilated, and the ball formed by the amnios is easily discovered; this ball is filled with a liquor, in the middle of which the head of the chicken and back-bone are distinctly seen. In about six hours more the little animal is seen more distinctly; in another six hours the head is grown larger, and the spine lengthened; and at the end of twenty-four hours the neck begins to lengthen, the vertebræ of the back appears of a white colour, and the head to turn to one side. The vertebræ are disposed on each side of the spine, like small globules; and almost at the same time the small wings begin to shoot, and the head, neck, and breast are lengthened. After thirty hours nothing new appears, but every part of the little animal is considerably increased, especially the amnios. Around this membrane the umbilical vessels are seen of a darkish colour. At the end of thirty-eight hours, the chicken being grown much larger, its head is large, and in which are distinguished three vessels surrounded with membranes, which also cover the back bone, through which the vertebræ are still seen. In forty hours, continues Malpighius, it was wonderful to see the chicken alive, floating in the liquor; the back bone was increased, the head was turned on one side, the vesicles of the brain were less apparent, the first outlines of the eyes appeared, the heart beat, and the circulation of the blood was begun. Malpighius then gives the description of the vessels and course of the blood, and reasonably supposes that, though the heart does not beat before thirty-eight or forty hours incubation, it still existed before that time, like the other parts of the chicken; but on examining the heart in a dark room, he discovered not the least glimpse of light to proceed from it, as Harvey insinuates.

At the end of two days the chicken is seen floating in the liquor of the amnios; in which the head, composed of vesicles, is turned on one side; the back bone and vertebræ are lengthened; the heart, which then hung out of the breast, beat three times; for the fluid it contains is impelled into the ventricles of the heart, from thence into the arteries, and afterwards into the umbilical vessels. He remarks, that having separated the chick from the white of the egg, the motion of the heart still continued for a whole day. After two days and fourteen hours, or sixty-two hours of incubation, the chicken, although grown stronger, remained with its head bent downwards in the liquor, contained by the amnios; the veins and arteries were seen among the vessels of the brain; the lineaments of the eyes, and the spinal marrow, also appear extending the length of the vertebræ.

At the end of the third day the head of the chicken appeared crooked; besides the eyes five vessels were seen in the head filled with a liquid matter; the first outlines of the wings and thighs were to be distinguished, and the body began to gather flesh; the pupil of the eye, and also the crystalline and vitreous humour were discernible. At the fourth day the vesicles of the brain were nearer each other; the eminences of the vertebræ were more prominent, the wings and thighs assumed a greater solidity as they increased in length; the whole body, covered with a jelly-like flesh, was now surrounded within the body by a thin membrane, and the umbilical vessels that unite the animal to the yolk, appeared to come from the abdomen. On the fifth and sixth days the vesicles of the brain began to be covered; the spinal marrow, divided into two parts, began to take solidity and stretch along the trunk; the wings and thighs lengthened; the feet began to spread; the belly was closed up and tumid; the liver was distinctly seen, and appeared of a dusky white; the ventricles of the heart were discerned to beat very distinctly; the body of the chicken was covered with a skin, and the traces of the feathers were visible; the seventh day the head appeared very large, the brain was entirely covered with its membranes; the beak began to appear betwixt the eyes, and the wings, the thighs, and the legs had acquired their perfect figure.

I shall not follow Malpighius any farther, as the remainder relates only to the expansion of the parts till the twenty-first day, when the chicken breaks the shell with its beak; though before that time it is heard to chirrup in its imprisonment. The heart is the last part which receives its proper form, for it is eleven days before the arteries are seen to join, and the ventricles become perfectly conformable and united.

We are now in a condition to judge of the value of Harvey's experiments and observations. There is great appearance this anatomist did not make use of a microscope, which in fact was not brought to perfection in his days, or he would not have asserted there was no difference between the cicatrice of an impregnated and an unimpregnated egg; he would not have said the seed of the male produced no alteration in the egg, especially in the cicatrice; he would not have affirmed that nothing was perceptible till the third day, that the animated speck was the first that appeared, and into which the white speck was changed. He would have seen that the white speck was a ball which contained the whole apparatus of generation, and that every part of the fœtus are there from the moment the hen has connection with the cock. He would also have learnt, that without this connection it contains only an unshapen mass, which could never become animated, because in fact it is not organized like an animal, and because it is only when this mass, which we must look upon as an assemblage of the organic particles of the female semen, is penetrated by the organic particles of the male semen, that there results from it an animal, which is formed at the moment, but whose motion is imperceptible till the end of forty hours after: he would not have asserted that the heart is first formed, and that the other parts are joined to it by a juxta-position, since it is evident from Malpighius's observations, that the outlines of every part are all immediately formed, but only appear in proportion as they dilate; on the whole, if he had seen what Malpighius saw, he would not have affirmed that no impression of the male seed remained in the eggs, and that it was only by contagion that they are fecundated, &c.

It is also just to remark, that what Harvey has said on the parts of the generation of a cock is not exact; he asserts that the cock has no genital member, and that there is no intromission; nevertheless it is certain that this animal, instead of one has two, and that they both act at the same time, and which action is a very strong compression, if not a true copulation;[I] and it is by this double organ that the cock emits the seminal liquor into the matrix of the hen.

[I] See Reyn. Graaf, page 242.

Let us now compare the experiments made by Harvey on hinds with those of De Graaf on doe rabbits; we shall find that although De Graaf supposes, with Harvey, that all animals proceed from eggs, yet there is a great difference in the mode which these two anatomists have observed in the first steps of formation, or rather expansion, of the fœtuses of viviparous animals.

After having exerted every effort to establish, by reasons drawn from comparative anatomy, that the testicles of viviparous females are real ovaries, De Graaf explains how the eggs are loosened from the ovaries and fall into the horns of the matrix; he then relates what he observed in a rabbit, which he dissected half an hour after copulation. The horns of the matrix, he says, were more red than before, but no other change in the rest of the parts: there was also no appearance of any male seed, neither in the vagina, matrix, nor horns of the matrix.

Having dissected another six hours after copulation he observed the follicules, or coats, which he supposes contained the eggs in the ovary, ware become red, but found no male seed either in the ovaria or elsewhere. He dissected another twenty-four hours after copulation, and remarked in one ovarium three, and in the other five follicules that were changed, the transparency being become dark and red. In one dissected twenty-seven hours after copulation he perceived the horns of the womb had become more red and strictly embraced the ovaries. In another, that he opened forty hours after copulation, he found in one of the ovaries seven, follicules, and in the other three that were changed. Fifty-two hours after copulation he examined another and found one follicle changed in one of the ovaries and four in another, and having opened these follicules he found a glandular liquor, in the middle of which there was a small cavity, where he did not perceive any liquor, which made him suppose that the transparent liquor, commonly contained in the follicules, and which, he says, is enclosed in its own membranes, might have been separated by a kind of rupture: he searched after this matter in the passages, and in the horns of the matrix themselves, but he found none; he only perceived that the internal membrane of the horns of the matrix was very much swelled. In another, dissected three days after copulation, he observed that the superior extremity of the passage, which communicates with the horns of the matrix, strictly embraced the ovaries; and having separated it he perceived three follicules, longer and harder than usual. After searching with the greatest attention the passages above-mentioned he found in the right passage one egg, and in the right horn of the matrix two more, not bigger than a grain of mustard-seed: those little eggs were each closed in double membranes, and the inner one was filled with a very limpid liquor. Having examined the other ovarium he found four follicules that were changed, three of which were white and had a little liquor within them; but the fourth was of a darker colour, and contained no liquor, which made him judge that from this the egg had been separated. Pursuing his enquiries he found an egg in the superior extremity of the other horn, and exactly like those he had discovered in the right one. He says that the eggs which are separated from the ovary are ten times smaller than those which are fastened to it; and he thinks that this difference is occasioned from the eggs containing, when they are in the ovaries, another matter, and that is the glandular liquor he remarked in the molecules.

Four days after copulation he opened another, and found in one of the ovaries four, and in the other three follicules, emptied of their eggs; and in the horns corresponding to these he found an equal number of eggs. These eggs were larger than the first that he found three days after copulation, and were about the size of a small bird-shot; he also remarked that the internal membrane in these eggs was separated from the external, and appeared like a second egg in the first. In another, dissected five days after copulation, he found five empty follicules in the ovaries, and as many eggs in the matrix, to which they adhered. These eggs were about the size of duck-shot, and the internal membrane was more apparent than in the one he had observed before. In one which he opened six days after copulation there were six empty follicules in one ovaria, and only five eggs in the corresponding horn, and they appeared in one mass; in the other ovaria were four empty follicules and but one egg; these eggs were as big as swan-shot. He opened another on the seventh day after copulation, and found seven empty follicules; he also perceived several internal tumours in the matrix, from whence he took eggs the size of a pistol-bullet. Its membrane was more distinct than before, but contained only a very clear liquor. In one, eight days after copulation, he found in the matrix tumours, or cells, which contained the eggs, but they were very adherent, for he could not loosen them. In another, nine days after copulation, the cells, which contained the eggs, were greatly increased, and he saw that the liquor inclosed by the internal membrane had now got a light cloud floating upon it. He opened another ten days after copulation and the cloud was thicker, and formed an oblong body, like a little worm. At last, on the twelfth day after copulation, the figure of the embryo was distinctly to be perceived, which two days before only presented the figure of an oblong body; it was even so apparent that the different members might be distinguished. In the region of the breast he perceived two red and two white specks, and in the abdomen a mucilaginous substance, somewhat reddish. Fourteen days after copulation the head of the embryo was become large and transparent, the eyes prominent, the mouth open, the rudiments of the ears appeared; the back-bone, of a whitish colour, was bent towards the breast, and small blood-vessels came from each side, whose ramifications ran along the back as far as the feet; the two red specks, being considerably increased, appeared to be no other than the ventricles of the heart; by the sides of these red specks were two white ones, which were the rudiments of the lungs. In the abdomen the outlines of the liver were seen of a reddish colour, and a little intricate mass, like a ravelled thread, which was the stomach and intestines. After this the process was no more than a growth and expansion of every part till the thirty-first day, when the female rabbit brings forth her young.

From these experiments De Graaf concludes, that all viviparous females have eggs; that these eggs are contained in the testicles, called ovaries; that they cannot disengage themselves till they are impregnated, because, he says, the glandular substance, by means of which the eggs quit their follicules, is not produced till after an impregnation. He also insists, that those who suppose they have seen eggs in only two or three days increased in size, must have been mistaken, for these eggs remain a longer time in the ovary, although fecundated, and instead of immediately increasing, they rather diminish until they are descended from the ovaries into the matrix.

By comparing these observations with those of Harvey, we shall easily perceive that the principal circumstances have escaped the latter; and although there are many errors in the reasoning and experiments of De Graaf, nevertheless this anatomist, as well as Malpighius, has made better observations than Harvey. They agree in the principal points, and are both contrary to Harvey; the latter had never seen the alterations which happen to the ovary; he did not see the small globules in the matrix which contain the apparatus of generation, and which De Graaf calls eggs. He had not even a supposition that the fœtus existed in this egg; and though his experiments gave us nearly an exact account of what occurs during the growth of the fœtus, they give us no information either of the moment of fecundation or of the first development. Schrader, a Dutch physician, who held Harvey in great veneration, owns that we must not put too great a reliance in that anatomist in many things, and especially on what he says of the fecundative moment, for the chicken in fact is in the egg before incubation, and that Joseph de Aromatarius was the first who observed it.[J] Although Harvey pretended that every animal proceeds from an egg, he did not imagine that the testicles of females contained these eggs, and has only repeated what Aristotle has said on this subject. The first who speaks of having discovered eggs in female ovaries is Steno, who says, in dissecting a female sea-dog he saw eggs in the testicles, although that animal is viviparous; and he adds, that the testicles of women are analogous to the ovaries of oviparous animals, whether the eggs fall in any manner into the matrix, or whether there only falls the matter they contain. Although Steno is the first who discovered these pretended eggs, De Graaf claims the merit to himself, and Swammerdam has disputed it with him, insisting that Van Horn had perceived these eggs before De Graaf. It is true this last writer stands charged with asserting many things experience has found to be false. He pretended that a judgment might be formed of the number of fœtuses contained in the matrix by the number of cicatrices, or empty follicules, in the ovary, which is not true, as we may see by the observations of Verrheyen,[K] and by those of M. Mery,[L] and by some of De Graaf's own observations, where he found fewer eggs in the matrix than cicatrices in the ovaries. Besides, we shall make it appear that what he says concerning the separation of the eggs, and the manner in which they descend into the matrix, is not exact; that no eggs exist in the female testicles; that what is seen in the matrix is not an egg; and that nothing can be worse founded than the systems endeavoured to be established on the observations of this famous anatomist.

[J] See Observ. Justi Schraderi, Amst. 1674.

[K] Vol. I. chap. iii. Brussels edit. 1710.

[L] Hist. of the Academ. 1704.

This pretended discovery of eggs in the testicles of females attracted the attention of most anatomists; they, however, only met with small bladders in the testicles of female viviparous animals, these they did not hesitate to look on as real eggs: they therefore gave the name of ovaries to the testicles, and called the vesicles eggs, They also said, with De Graaf, that there are eggs of different sizes in the ovarium; that the largest in the ovarium of women was not above the size of a small pea; that they were very small in the young, but increased with age and intercourse with men; that twenty might be counted in each ovarium; that these eggs are fecundated in the ovarium by the spirited part of the seminal liquor of the male; that afterwards they loosen and fall into the matrix, where the fœtus is formed, from the internal substance of the egg and the placenta of the external matter; that the glandular substance, which does not exist in the ovarium till after a fruitful copulation, serves to compress the egg, and make it quit the ovarium, &c. But Malpighius having examined things more minutely, detected many of their errors before they were even received; yet most physicians adopted the sentiments of De Graaf, without any attention to the observations of Malpighius; which, notwithstanding, are very important, and to which his scholar Valisnieri has given a great deal of weight.

Malpighius and Valisnieri, of all naturalists, speak with the greatest foundation on the subject of generation. We shall therefore give an account of their experiments and remarks, to which we cannot pay too much attention.

Malpighius having examined a great number of the testicles of cows and other female animals, affirms that he found vesicles of different sizes in the testicles of all of them, whether young or adults; these vesicles are inclosed by a thick membrane, in the inner parts of which there are blood-vessels, filled with a kind of lymph, or liquor, which hardens by the heat of the fire like the white of an egg.

In time a firm yellow body grows which adheres to the testicles. It is prominent and increases to the size of a cherry, occupying the greatest part of the ovarium. The body is composed of many little angular tubes, and its position is irregular; it is covered with a coat, or membrane, spread over with nerves and blood-vessels. The appearance and form of this yellow body are not always the same, but vary according to time. When not above the size of a millet seed, it is nearly globular, and if divided appears composed of a kind of variegated net-work. Very often an external covering is observed, composed of the same substance as the yellow body, around the vesicles of the ovarium.

When the yellow body is become nearly of the size of a pea, it is the shape of a pear, in which is a small cavity filled with liquor; as is also the case when grown to the size of a cherry. In some of these yellow substances, when increased to their full maturity, Malpighius says, a small egg, with its appendages, not bigger than a millet seed, may be seen near the centre; when they have cast out their eggs they are empty, resemble a cavernous passage, and the cavities which inclose them are about the size of peas. He thinks this yellow and glandular substance nature produces to preserve the egg, and assist it in leaving the testicles, and perhaps to contribute towards the generation of the egg itself; consequently, he says, the vesicles, which are always observed in the ovary, and which are of different sizes, are not real eggs that may be fecundated, but only serve for the production of the yellow body where the egg is to be formed. On the whole, although these yellow substances are not found at all times in all testicles, we nevertheless always find the first traces of them, and Malpighius having seen the marks of them in young heifers, cows that were with calf, and in pregnant women, he reasonably concludes that this yellow and glandular substance is not, as De Graaf has supposed, the effect of fecundation, but what produces the infecund eggs, which leave the ovary without any communication with the male, as well as to those which leave it after communication. When the latter falls into the tubes of the matrix, all the rest is performed as De Graaf has described.

These observations of Malpighius shew that the testicles of females are not real ovaries, as most anatomists believe; that the vesicles they contain are not eggs; that these vesicles never fall into the matrix; and that the testicles, like those of the male, are kinds of reservoirs, containing a liquor which must be looked upon as an imperfect seed of the female, that is perfected in the yellow glandular body which fills the internal cavity, and is shed when the glandular substance has acquired its full maturity. But before we decide on this important point, we must relate the observations of Valisnieri; and we shall perceive that, though Malpighius and Valisnieri have made good observations, they have not carried them far enough, nor drawn those consequences from them which their observations might naturally have produced, because they were both prejudiced for the system of eggs, and of the fœtus pre-existing therein.

Valisnieri began his experiments in 1692, on the testicles of a sow, whose testicles are not composed like those of a cow, sheep, mare, bitch, female ass, she goat, nor most other viviparous females, for they resemble a small bunch of grapes, whose seeds are round and prominent outwardly. Between these seeds there are smaller, which have not arrived to maturity. These seeds do not appear to be surrounded with one common membrane; they are, he says, similar to those yellow substances which Malpighius observed in cows; they are round, of a reddish colour, their surface sprinkled over with sanguinary vessels like the eggs of viviparous animals, and together form a mass larger than the ovary; we may, with a little address, and by dividing the membrane, separate these grains one by one, and draw them from the ovary, where they each leave an impression.

These glandular substances are not of the same colour in every sow, in some they are red, in others more clear; and they are of all sizes, from the most minute point to that of a grape. On opening them we find a triangular cavity filled with a limpid liquor, which coagulates by the fire, and becomes white like that contained in the vesicles. Valisnieri hoped to meet with the egg in one of those cavities, but although he sought for it with the utmost assiduity in the glandular substance of the ovaries of four different sows, and afterwards in those of other animals, yet he could never discover the egg which Malpighius asserts to have met with once or twice.

Below these glandular substances the vesicles of the ovary were seen, and which were in a greater or lesser number as the glandular substances are thicker or smaller, for in proportion as the glandular substances increase, the vesicles diminish. Some of these vesicles were the size of a lentil, and others as small as a millet-seed. In crude testicles twenty, thirty, or thirty-five vesicles might be counted, but when boiled a greater number are seen; and they are so strongly connected by fibres and membraneous vessels, that it is impossible to separate them without a rupture.

Having examined the testicles of a sow which never had littered, he found there, as in the rest, glandular bodies, and their triangular cavities filled with lymph, but never met with the egg either in the one or the other. The vesicles of this sow which had never littered were greater in number than in those which had littered or conceived. In the testicles of another sow which had conceived, and whose young were much expanded, he found two large glandular substances, that were empty, and others smaller, in their common state. Having also dissected many others when with young, he found that the number of glandular substances was always greater than that of the fœtus, which confirms our observations on De Graaf's experiments, and proves they are not exact; what he terms the follicules of the ovary being only the glandular substances, whose number always exceed that of the fœtus. In the ovaries of a sow but a few months old, the testicles were large, and sprinkled with vesicles pretty well tumefied: between these vesicles there were four rising glandular substances in one of the testicles, and more in the other.

After having finished his experiments on sows, Valisnieri repeated those of Malpighius on the testicles of cows, and found that all he had said was conformable to truth; only Valisnieri owns that he has never been able to find the egg which Malpighius thought he had seen once or twice in the internal cavity of glandular bodies. Valisnieri proceeded in his experiments upon a variety of other animals to discover this egg, but in vain; nevertheless his prejudice for that system induced him, contrary to his experience, to admit the existence of eggs, which neither he nor any other man ever did or ever will see. It is scarcely possible to make a greater number of experiments, or better than he has done. He observes, as something particular to a ewe, that there are never more glandular substances in the testicles than fœtuses in the matrix. In young ewes, which have never been with the male, there is but one glandular substance in each testicle, which when worn away, another is found; and if a ewe has only one fœtus in her matrix, there is but one glandular substance in the testicles; if there are two fœtuses there will be two glandular substances. This substance occupies the greatest part of the testicles; after it disappears another is formed for the purpose of another generation.

In the testicles of a she-ass he perceived vesicles the size of small cherries, which evidently prove they are not eggs, since, being of that size, they could not enter into the horns of the matrix, which are too narrow in this animal for their reception.

The testicles of a female dog, wolf, or fox, have a kind of cowl, or covering, which is produced by the expansion of the membrane that surrounds the horns of the matrix. In a bitch, whose heat was just began, and had not been brought to a dog, Valisnieri found this cowl, which is not adherent to the testicle, internally bathed with a liquor like whey: he discovered also two glandular substances in the right testicle, which run almost its whole length. These glandular substances had each a small nipple, with a little orifice, from which of itself issued a clear liquor like whey, and when pressed, a greater quantity came out, which made him imagine, that this liquor was the same as that found within the cowl: he blew into this orifice, by the means of a small pipe, and immediately the glandular body was puffed up; and having introduced a bristle, he easily penetrated to the end of it: he opened this glandular substance the same way as the bristle was entered, and found within a cavity which communicated with the orifice, and which also contained a good deal of liquor. Valisnieri was also in hopes to discover the egg, but, notwithstanding all his endeavours and strict attention, he never could perceive it. He remarked, that the extremity of these nipples, from which this liquor flowed, was contracted by a sphincter, which served to shut up, or open the orifice of the nipple: he found also in the left testicle two glandular bodies with the like cavities, nipples, orifices, and liquor distilling from them. Still not being able to find the egg, neither in this liquor, nor in the cavity which contained it, he boiled two of these glandular substances, hoping that by this means he might discover the object he was in pursuit of, but it was all in vain.

Having opened another bitch, eight or nine days after she had been with the male, he found no difference in the testicles; there were three glandular substances like the preceding ones, and, like them, distilled a liquor from the nipples. Here he also persevered in his fruitless researches after the egg. By the help of a microscope, he perceived the glandular substances were a kind of vascular net-work, formed by an infinite number of small globular vesicles which served to filtre the liquor that issues through the end of the nipple.

After this he opened another bitch whose heat was off, and having introduced air between the testicle and its covering, he found it dilated like a bladder by means of inflation; having raised this cowl, he found three glandular substances on the testicle, but they had no apparent nipple, nor orifice, nor did any liquor distil from them.

In another bitch that had pupped two months, and had five puppies, he found five glandular substances, which were become very small, and began to obliterate, without leaving any cicatrices: there still remained a small cavity in the middle, but it was dry and empty.

Not content with these, and many more experiments, Valisnieri, who would not give up his researches after the pretended egg, called together the most expert anatomists of his country, among whom was M. Morgagni, and having opened a young bitch at the time of her first heat, and had been with a male three days before, they examined the vesicles of the testicles, the glandular substances with their nipples, orifice, and liquor which flowed from them, and in their internal cavities, but not an egg was to be found. After this he made experiments on female goats, foxes, cats, and a great number of mice, &c. He always found vesicles in the testicles of all those animals, and often the glandular substances, and the liquor they contained, but never any egg.

At length, desirous of examining the testicles of a woman, he had an opportunity of opening a farmer's wife, a young woman that was killed by a fall from a tree. She had been married several years, but although of a good habit of body, yet she had never borne a child. He sought if the cause of her sterility was not discoverable in the testicles; and he found the vesicles all replete with a blackish and corrupted matter.

In the testicles of a girl of eighteen, who had been brought up in a convent, and, according to all appearances, was a virgin, he found the right testicle somewhat larger than the left: its shape was oval, and its surface a little unequal. This inequality was produced by the protuberance of five or six vesicles of this testicle which advanced forwards; one of which was more prominent than any of the rest. Having opened this vesicle, a spirit of lymph issued out: around it there was a glandular substance in form of a crescent of a yellowish colour rather bordering on the red. He cut the remainder part of the testicle transversely, and found many vesicles filled with a limpid liquor, and remarked that the corresponding trunk to this testicle was very red and a little longer than the other, as he had frequently observed in female animals, when in their amorous season.

The left testicle was as round as the right, it was whiter, and its surface more smooth; for although there were some vesicles a little prominent, yet there were not any in form of a nipple; they were all alike, without any glandular substance, and the corresponding trunk was neither inflamed nor red.

In a little girl of five years old, he found the testicles with the vesicles, blood vessels, fibres and nerves complete.

In the testicles of a woman sixty years of age, he found some vesicles, and the vestiges of a glandular substance, which were as so many thick points of matter of a dark brownish colour.

From all these observations Valisnieri concludes, that the business of generation is carried on in the female testicles, which he looked upon as ovaries, although he never found any eggs in them, but on the contrary, evidently saw that the vesicles were not eggs. He also says, that it is not necessary for the seed of the male to enter into the matrix to impregnate the egg: he supposes that the egg comes from the nipple of the glandular substance, after impregnation in the ovarium; that from thence it falls into the trunk, and descends by degrees, till at last it fastens to the matrix. He adds, he is persuaded that the egg is concealed in the glandular substance, and that all the business of generation is performed in the cavity, although neither he nor any other anatomist, have ever seen or been able to find it.

According to Valisnieri the spirit of the male seed ascends to the ovarium, forces its way into the egg, and gives motion to the fœtus that pre-exists therein. In the ovarium of the first woman were eggs, which not only inclosed in miniature every child she brought forth, but of the whole human race. That if we cannot conceive this infinite chain of individuals contained in one, it is the fault of our minds, the weakness of which is every day perceptible; but it is, upon that account, no less true, that every animal which has been, is, and will be, were created all at one time, and inclosed in the first females. The resemblance of children to parents only proceeds, continues he, from the imagination of the mother, the power of which is so great on the fœtus that it can produce on it spots, marks, disproportions, and extraordinary births, as well as perfect resemblances.

This system of the eggs, which is unreasonable, and without foundation, would, nevertheless, have obtained the unanimous suffrages of all physicians, if, when it was first endeavoured to be established, another system had not been formed on the discovery of spermatic animals.

This discovery, for which we are indebted to Leeuwenhoeck and Hartsoeker, has been confirmed by Andri, Valisnieri, Bourguet, and many other observers of Nature. I shall relate what has been said concerning the spermatic animals which are found in the seminal liquor of all males: they are in such vast numbers that the semen seems to be entirely composed of them; and Leeuwenhoeck pretends to have seen many millions of them in a drop smaller than the smallest grain of sand. Although we do not meet with any in female animals they abound in all males, both in the semen emitted naturally and that in the testicles, as well as in the seminal vesicles. If the semen of a man is exposed to a moderate heat it thickens, and the motions of all the animalcules immediately cease, but if allowed to cool it becomes thinner, and the animals preserve their motion till the liquor thickens as it dries away. The thinner the liquor becomes the more the animalcule increase, and if water is added it will appear like a substance of small animals. When the motion of these animalcule is nearly finished, whether from heat, or any other cause, they seem to assemble closer together, and have a whirling motion in the centre of a small drop which may have been taken out for observation, and appear all to perish at one and the same time, whereas in the larger portion of the liquor they are easily seen to perish successively.

The animalculæ, say they, have different figures in different animals; nevertheless they are all long, slender, without any appearance of limbs, and move with rapidity. The fluid which contains them, as we have already observed, is heavier than blood. The semen of a bull afforded Verrheyen, by a chemical process, first phlegm, afterwards a considerable quantity of fœtid oil, but little volatile salt, and much more earth than he could have thought.[M] This author appears surprised that in rectifying the distilled liquor he could not draw any spirit from it, and being persuaded it contained a great quantity, he attributed the evaporation to its great subtility: but may it not be more reasonably imagined that it contains very little or no spirits, as neither its consistency nor smell announce any ardent spirit, and which is only plentifully found in fermented liquors? besides, with respect to volatile spirits, the horns, bones, and other solid parts of animals, afford more than all the liquor of the animal body. What anatomists have called animal spirits, aura seminalis, may possibly not exist; and it is certainly not these spirits which agitate the particles seen moving in the seminal liquors; but we will here relate the principal observations that have been made on this subject.

[M] See Veerheyen, sup. anat. tom. ii. page 69.

Leeuwenhoeck observed, in the semen of a cock, animals which resemble the figure of an eel, but so exceedingly minute, that he pretends fifty thousand would not equal in size a grain of sand; and in that of a rat many millions would be required to make the thickness of a hair, &c. This observer imagined that the whole substance of the semen was only a mass of these animalcules. He perceived these animalculæ in the semen of men, quadrupeds, birds, fishes, insects, &c. In that of grasshoppers they were long and slender. They are attached, he says, by their extremities, and the inferior of which he calls the tail, had a quick motion, like that of the tail of a serpent, when the upper part is motionless. He further adds, that in the semen of young animals the animalculæ are motionless, but as the age for reproduction comes on they move about with great vivacity.

In the semen of a male frog he observed animalculæ, at first they were imperfect and motionless, but some time afterwards he found them living: they were so very small, he says, that ten thousand would scarcely equal the size of a single egg of the female. It was only those in the seminal liquor of the frog which had life and motion.

In the semen of a man, and that of a dog, he pretends to have seen two kinds, which he looked upon as males and females. Having inclosed the seed of a dog in a vial, he says, that numbers of the animalculæ died the first day; the second and third there died still more, and very few remained alive the fourth. But having repeated this experiment on the semen of the same dog, he found, at the end of seven days, live animalculæ, some of which swam with as much swiftness as in fresh-extracted semen; and having opened a bitch which had been three times with the same dog, he could not perceive by the naked eye any seminal liquor of the male in either of the horns of the matrix; but by help of a microscope he discovered the spermatic animals of the dog in both horns of the matrix, and great numbers of them in that part of the matrix adjoining to the vagina, which, says he, evidently proves that the male semen enters the matrix, or at least that the spermatic animals of the dog had got there by their own motion, which is sufficient to carry them four or five inches in half an hour. In the matrix of a doe rabbit, which had just received the buck, he likewise observed an infinite number of spermatic animals; he says, that their bodies are round, with long tails, and that they often change their forms, especially when the humid matter in which they swim evaporates and dries.

Leeuwenhoeck's experiments have been frequently repeated and found conformable to truth. There have been some inclined to exceed him in these discoveries. Dr. Dalenpatius having observed the seminal liquor of a man, not only pretended to have discovered animals like tadpoles, whose bodies appeared nearly the size of a grain of wheat, and their tails four or five times longer than their bodies, and which moved with great agility, but, what is still more marvellous, he observed one of these animals quit its covering; upon which it was no longer an animalcule, but had become a human body, the two legs of which, he affirms, were very discernible, as were the arms, breast, and head.[N] But by the figures which this author has given of this pretended embryo, it is evident his assertion is false. He might suppose he saw what he relates, but he was mistaken; for the embryo, such as he describes, was more formed on quitting this covering, and the state of a spermatic worm, than it would have been at the end of a month or five weeks in the matrix of its mother; therefore this observation of Dalenpatius, instead of having been confirmed by other observations, has been rejected by every naturalist, the most exact and accurate of which have only discovered, in the seminal liquor of man, round and oblong bodies, which seemed to have long tails, but without any kind of members.

[N] See Nouvelles de la Republique des Lettres, Ann. 1699, page 552.

It might be said that Plato had spoken of these spermatic animals which become human forms; for he says, "Vulva quoque matrix que in fœminis eadem ratione animal avidem generandi, quando procul a fœtu per ætatis florem, aut ultra diutius detinetur, ægre fert moram ac plurimum indignatur, passimque per corpus oberrans, meatus spiritus intercludit, respirare non finit, extremis vexat angustiis, morbis denique omnibus premit, quosque atrorumque Cupido amorque quasi ex arboribus fœtum fructumve producunt, ipsum deinde decerpunt, & in matricem velut agrem inspargunt; hinc animalia primum talia, ut nec propter parvitatem videantur, necdum appareant formata, concipiunt: mox quæ conflaverant, explicant, ingentia, intus enutriunt, demum educunt in lucem, animaliumque generationem perficiunt." Hippocrates, in his treatise De Diæta, seems also to insinuate, that the seed of animals is replete with animalcules. Democritus speaks of certain worms which take the human figure, and Aristotle says, that the first men came out of the earth in the form of worms; but neither the authority of Plato, Hippocrates, Democritus, Aristotle, nor the observation of Dalenpatius, can make us receive the idea that these spermatic worms are small human bodies, concealed under a covering; for it is evidently contrary to experience and observation.

Valisnieri and Bourguet, whom we have quoted, discovered small worms in the seed of a rabbit, one of whose extremities was thicker than the other; they were very lively and active, struck the liquor with their tails, and twisted and turned themselves like snakes. At last (says Valisnieri) I clearly perceived them to be real animals, "e gli riconobbi, e gli giudicai senza dubitamento alcuno per veri, verissimi arciverissimi vermi[O]." This author, who was prejudiced with the system of eggs, has, nevertheless, admitted of spermatic worms, and taken them for real animals.

[O] Opere dell. Cav. Valisnieri, vol. II. page 105.

M. Andry having made observations on these spermatic worms of a man, pretends that they are only found in the age proper for generation; that in the younger years, and in old age, they do not exist: that in those affected with venereal disorders there are very few, and those are languishing, and for the most part dead: that in impotent persons we do not see any alive; that these worms in the semen of men have larger heads than in that of other animals, which agrees, he says, with the figure of the fœtus and the child; and he adds, those people who too frequently enjoy female amours, have generally but few or none of these animalcules in their semen.

Leeuwenhoeck, Andry, and many others, strenuously opposed the egg system; they had discovered in the semen of all males living animalcules; they proved that these animalcules could not be regarded merely as dwelling in this liquor, since their bulk was greater than that of the liquor itself; and that nothing like them was found either in the blood, or in the other animal liquors. They asserted, that females furnished nothing similar, nothing alive; and it was therefore evident that the fecundity attributed to them belonged, on the contrary, to males alone: and that the discovery of these spermatic animals in the semen tended more to the explanation of generation than all that had been before supposed; since, in fact, what was most difficult to conceive in generation, was the production of the living part, all the rest being only accessary operations, and therefore no doubt could remain but these little animals were destined to become men, or perfect animals of their kind. When it was opposed to the partizans of this system, that it did not seem natural to suppose that so many millions of animalcules, every one of which might become a human being, should be employed for a purpose of which one alone was to reap the advantage; when it was asked them, why this useless profusion of the shoots of human beings? they answered, that it was only consonant with the common munificence of nature: that out of many millions of seeds which plants and trees produce, but a very few succeed, and therefore we must not be surprised at the same circumstance in spermatic animals. When the infinite minuteness of the spermatic worm, compared to man, was objected to them, they answered, by the example of the seed of trees; and they added, with some foundation, metaphysical reasonings, by which they proved that great and small being only relations, the transition from small to great, or from great to small, was executed by nature with still more facility than we can conceive.

Besides, continue they, have we not very frequent examples of transformation in insects? do we not see small aquatic worms become winged animals, by only throwing off their coats, which were their apparent and external forms? and may not spermatic animals, by a similar transformation, become perfect animals? All therefore, they conclude, concurs to favour this system of generation, and confuting that founded on eggs; and if there are eggs in viviparous females, the same as in the oviparous, these eggs will only be the necessary matter for the growth of the spermatic worm, which enters into the egg by the pedicle that adheres to the ovarium, and where it meets with food ready prepared for it. All the worms which find not this passage through the pedicle into the egg will perish, and that one which alone has traced its way will arrive at its transformation. The difficulty of meeting with the passage in the pedicle of the egg, can only be compensated by the infinite number of spermatic worms. It is a million to one that any particular spermatic worm will meet with the pedicle of the egg, and therefore what at first appears a profusion is highly necessary. When one has entered, no other can introduce itself, because, say they, the first worm entirely shuts up the passage, or there is a valve at the entrance of the pedicle, which is free when the egg is not absolutely full; but when the worm has filled the egg, the valve can no longer open although impelled by another worm. This valve is very well imagined, because, if the first worm should chance to return, it opposes its egress, and obliges it to remain and undergo the transformation. The spermatic worm then becomes the fœtus, the substance of the egg its food, the membranes, its covering, and when the nutriment in the egg is nearly exhausted, the fœtus adheres to the internal skin of the matrix, and thus derives nourishment from the parent's blood, till by its weight, and augmentation of its strength, it breaks through its imprisonment, and comes perfect into the world.

By this system it was not the first woman who inclosed all mankind, but the first man who contained all posterity in his body. The pre-existing germs are no longer embryos without light, inclosed in the eggs, and contained one in another, ad infinitum; but they are small animals, the little homunculæ organized and actually living, included in each other in endless succession, and to which nothing is wanting for them to become perfect animals, and human beings, but expansion, assisted by a transformation similar to that which winged insects undergo.

As our present physicians are divided on these two systems of spermatic worms and eggs, and as all those who have lately written on generation have adopted one or the other of these opinions, it seems necessary to examine them with care, and to shew that they are not only sufficient to explain the phenomena of generation, but are also founded on suppositions void of all probability.

Both suppose an infinite progression; which, as we have said, is not so much a reasonable supposition as an illusion of the mind. A spermatic worm is more than a thousand million times smaller than a man; if, therefore, we suppose the body of a man as an unit, the size of the spermatic worm can only be expressed by the fraction 1/1000000000; and as man is with respect to the spermatic worm of the first generation, what this worm is to that of the second generation, the size of the last spermatic worm cannot be expressed but by a number composed of nineteen cyphers; and so likewise the size of the spermatic worm of the third generation will require 28 cyphers; that of the fourth generation 37; the fifth 46, and the sixth 55 cyphers. To form an idea of the minuteness represented by this fraction, let us take the dimensions of the sphere of the universe from Sol to Saturn, and supposing the sun a million times larger than the earth, and about a thousand solar diameters distant from Saturn, we shall perceive that only 45 cyphers are required to express the number of cubic lines contained in this sphere; and, by reducing each cubic line into a thousand millions of atoms, 54 cyphers are only required to express that number; consequently a human being will be greater, with relation to a spermatic worm of the sixth generation, than the sphere of the universe is with relation to the smallest atom which is possible to be perceived by the assistance of a microscope. What would it be if we were to carry it to ten generations? The minuteness would be so great as to leave us no mode of expressing it. The probability of this opinion, therefore, evidently disappears in proportion as the object diminishes. This calculation may be applied to eggs as well as spermatic worms, and the want of probability is general to both; it will, no doubt, be said, that matter being divisible, ad infinitum, there is no impossibility in this diminution of size; and although it is not probable, yet we must regard this division of matter as possible, since we can always, by thought, divide an atom into a number of parts. But I answer, that the same illusion is made use of on this infinite divisibility as on every other geometrical and arithmetical infinity; they are only abstractions of the mind, and have no existence in nature. If we look on infinite divisibility of matter as an absolute infinity, it is easy to demonstrate that in that sense it does not exist; for, if once we suppose the smallest atom possible, by that supposition this atom will necessarily be indivisible, since if it were divisible it would no longer be the smallest atom possible, which would be contrary to the supposition. It therefore seems to me, that every hypothesis where a progress, ad infinitum, is admitted, ought to be rejected not only as false, but as void of all probability; and as the system of eggs and spermatic worms supposes this progress, they should not be admitted in philosophy.

Another great difficulty against these two systems is, that in the egg system the first woman contained the male and female eggs: the male eggs contained only a generation of males; and that, on the contrary, the female eggs contained thousands of generations, both of males and females; insomuch that, at the same time, and in the same woman, there was always a certain number of eggs capable of developing themselves to infinity, and another number which would be unfolded but once. The same circumstance must occur in the other system, and therefore I ask if there is the smallest appearance of probability in these suppositions?

A third difficulty arises against these two systems, which is, the resemblance that children bear, sometimes to the father and sometimes to the mother, and sometimes to both; and the evident marks of extraordinary difference in mules, &c. If from the spermatic worm of the father the fœtus is produced, how can the child resemble the mother; and if the fœtus is pre-existing in the egg of the mother, how can the child resemble its father? or if the spermatic worm of a horse, or the egg of a she-ass contains the fœtus, how can the mule participate in the nature and figure of both the horse and the ass?

These general difficulties, which are invincible, are not the only ones that can be made against these systems; there are particular ones which are no less potent. To begin with the system of spermatic worms, may it not be asked of those who admit of it, how they think this transformation is made? and object to them, that insects have not, nor cannot have any relation with what they suppose. For the worm which is to become a fly, or the caterpillar which is to become a butterfly, passes through a middle state, and when it ceases to be a chrysalis, it is completely formed and has acquired its full size, and is then in a condition of engendering; whereas in the pretended transformation of the spermatic worm into man, it cannot be said to be in a state of chrysalis, and even if we should suppose one during the first days of conception, why does not the production of this chrysalis, instead of an unformed embryo, suppose an adult and perfect being? We plainly see how analogy is here violated; and that far from confirming this idea of the transformation of the spermatic worm, it is instantly destroyed by examination.

Besides, the worm which is transformed into a fly proceeds from an egg; the egg is the produce of the copulation of the male and female, and includes the fœtus, which must afterwards enter into a chrysalis, before it arrives at its state of perfection, as a fly; in which form alone it has an engendering power; whereas the spermatic worm has no faculty of generation, nor proceeds from an egg. Even should we allow the semen to contain eggs, from whence issue spermatic worms, the same difficulty will still remain, for these supposed eggs have not the copulation of the two sexes for their principle of existence, as in insects; consequently the partizans of that opinion cannot pretend any similarity, nor derive any advantage from the transformation of insects; which rather destroys the basis of their explanation.

When the innumerable multitude of spermatic worms are opposed to those physicians who are prejudiced by this system, they answer, as before observed, by the examples of plants and trees. But this comparison is not entirely just, because all the spermatic worms excepting one perish by absolute necessity, which is not the case with the seeds of a tree or plant, for those which do not become vegetables, serve as food for other organized bodies, and for the expansion and reproduction of animals; whereas we do not see any use for the spermatic worms, or any end to which we can refer their prodigious superfluity. On the whole, I only make this remark in reply to what is, or may be said on this matter; for I own, that no arguments drawn from final causes will either establish or destroy a physical system.

Another objection made against this opinion is, there being, to all appearance, an equal number of separate worms in the seed of all kinds of animals, for, say they, it is natural to imagine, that in those kinds where fœtuses are most abundant, as in fishes, insects, &c. the number of spermatic worms should be more numerous than in those where generation is least abundant, as in man, quadrupeds, birds, &c. for if they are the immediate cause of production, why is there no proportion between their number and that of the fœtus? Besides, there is no proportionable difference in the size of most kinds of spermatic worms, those of large animals being as small as those of the least. Those of a rat, and those of a man, are nearly the same, and when there is any difference it is no ways relative to the size of the individual. The Calmar, which is a very small fish, has spermatic worms above one hundred thousand times larger than those of a man or a dog. Another proof these worms are not the immediate and only cause of generation.

The particular difficulties that may be raised against this egg system are no less considerable. If the fœtus exists in the egg before the communication of the male with the female, why do we not perceive the fœtus as well in those eggs produced before as after copulation? We have before recounted the observations of Malpighius, who says he always found the fœtus in those eggs produced by hens that had received the cock, and only a mass or mole in the cicatrice of those who had not; it is therefore very clear that the fœtus does not exist in the egg till after impregnation.

Another difficulty against this system is, that not only the fœtus is not seen in eggs before the junction of the sexes, but even the existence of eggs in viviparous animals is by no means proved. Those physicians who pretend that the spermatic worm is the fœtus enveloped in a covering, are at least assured of spermatic worms; but those who affirm that the fœtus is pre-existing in the egg, have no proof of the existence of the egg itself; on the contrary, there is a probability, almost equivalent to a certainty, that these eggs do not exist.

Although the partizans of the egg system do not agree what must be looked on as the true egg in the female testicle, nevertheless they all think that impregnation is made in the testicle called the ovarium, without paying any attention that if it was so most fœtuses would be found in the abdomen instead of the matrix, for the superior extremity of the trunk being separated from the ovarium, the pretended eggs must often fall into the abdomen. Now, it is certain that this case is extremely rare, and, I believe, never happened, unless occasioned by some accident.

The general difficulties and objections against these two systems have been noticed by the author of Venus Physique, whose treatise, although very short, has more philosophical ideas than there are in many folio volumes on generation. As this book is very public, and the accuracy with which it is written will not permit any extract, I shall only observe, this author is the first who has returned into the road of truth, from which we were farther strayed than ever, since the supposition of the egg system, and the discovery of spermatic animals. Nothing therefore remains farther to be said, and I shall conclude with relating a few particular experiments, some of which have appeared favourable, and others contrary, to these systems.

In the History of the Academy of Sciences of Paris, 1701, some objections are proposed by M. Mery against the egg system. This able anatomist supports, with reason, that the vesicles found in the female testicles are not eggs, but are so adherent to the internal substance of the testicle that they cannot be naturally separated therefrom; that if they could separate themselves from this substance it would be impossible for them to get out, because the common membrane, which surrounds all the testicle, is a web of too firm a texture to admit of a conception; that a vesicle, or round soft egg, could open a passage in it; and as the greatest number of physicians and anatomists were prejudiced in favour of the egg system, and, from the experiments of De Graaf, believed that the number of cicatrices in the testicles marked the number of fœtuses, M. Mery mentions the testicles of a woman, where there was such a quantity of these cicatrices, that, agreeable to this system, would have supposed a fecundity almost beyond imagination. These difficulties excited other partizans of the egg system to make new researches. M. Duverney examined and dissected the testicles of cows and sheep: he pretended that the vesicles were eggs, because there were some less adherent to the testicles than others, and insisted it was natural to believe, that when they came to perfect maturity they were separated altogether, especially as by inflating the internal cavity of the testicle the air passed between these vesicles and the adjoining parts. M. Mery only answers that this not a sufficient proof, since these vesicles have never been seen separate from the testicles. M. Duverney remarked the glandular bodies on the testicles, but he did not look on them as an essential and necessary part towards generation, but merely as accidental exuberances, like gall-nuts, on the oak. M. Littre, whose prejudice for the egg system was still greater, pretended, not only that the vesicles were eggs, but even asserted he had discovered in one of them a well-formed fœtus, of which he distinguished the head and trunk very perfectly, and even gave the dimensions. But besides this wonder being only seen by that gentleman, and no other naturalist, it is sufficient to read his Memoire[P] to perceive how doubtful was the fact. By his own words we find the matrix was schirrhous, that the testicle was corrupted, and that the vesicle, or egg, which contained this imaginary fœtus was smaller than the other vesicles, or eggs, which did not contain any thing, &c.

[P] Anno 1701, page 3.

A famous experiment, in favour of the egg system, is supplied by De Nuck; he opened a bitch three days after copulation; he drew out one of the horns of the matrix, and made a ligature in the middle, so that the upper part of the passage could have no communication with the lower; after which he replaced this horn, and closed up the wound, with which the bitch seemed but little incommoded. At the end of twenty-one days he opened it again, and found two fœtuses in the upper part, that is between the testicles and the ligature; but in the lower part there was no fœtus. In the other horn of the matrix, which had not been tied by a ligature, he found three fœtuses, which were regularly disposed, which proves, he says, that the fœtus does not proceed from the seed of the male, but exists in the female egg. Supposing this experiment, which has only been made once, was always followed with the same effect, we should not then be right in concluding that fecundation is made in the ovary, and that eggs are detached therefrom which contain the fœtus completely formed. It would only prove that the fœtus may be formed in the upper parts of the horns of the matrix as well as in the lower; and it seems very natural to imagine that the ligature, compressing the middle of the horns of the matrix, impelled the seminal liquors, which are in the lower parts, to issue out, and thus destroy the business of generation in them.

Thus we have gone through the opinions of anatomists and physicians on the subject of generation; and it now only remains for me to recount what I have been enabled to draw from my own researches and experiments, and it will then be seen whether my system is not infinitely more agreeable to Nature than any of those I have given an account of.

[CHAPTER VI.]

EXPERIMENTS ON THE METHOD OF GENERATION.

I often reflected on the above system, and was every day more and more convinced that my theory was infinitely the most probable. I then began to suppose that, by a microscope, I might be able to attain a discovery of the living organic particles, from which I thought every animal and vegetable drew their origin. My first supposition was, that the spermatic animalcules seen in the seed of every male, might possibly be these organic particles; on which I reasoned as follows:

If every animal and vegetable contain a quantity of living organic particles, these particles would be found in their seed, and in a greater quantity than in any other substance, because the seed is an extract of what is most analogous to the individual, and the most organic; and the animalcule we see in the seed of males are, perhaps, only these same living organic molecules, or at least the first union, or assemblage of them. But if this is so, the seed of the female must also contain similar living organic molecules, and, consequently, we ought to find moving bodies there as well as in the male: and since the living organic particles are common both to animals and vegetables, we should also find them in the seeds of plants, in the nectarium, and in the stamina, which are the most essential parts of vegetables, and which contain the organic molecules necessary for reproduction. I then seriously thought of examining the seminal liquors of both sexes, and the germs of plants, with a microscope. I thought, likewise, that the reservoirs of the female seed might possibly be the cavities of the glandular bodies, in which Valisnieri and others had uselessly sought for the egg; and at length determined to undertake a course of observations and experiments. I first communicated my ideas to Mr. Needham, a gentleman well known for his microscopical observations, and read to him the first part of this work; he seemed to approve of these ideas, and did me the favour to lend me his microscope which was infinitely superior to my own. At the same time I communicated my system and project of experiments to Messrs. Daubenton, Gueneau, and Dalibard, all of whom encouraged me to persevere in my determination, and from whom, in the course of making those experiments, I received much assistance, particularly from Mr. Daubenton.

Persons not experienced in the use of the microscope will not be displeased that I here insert some remarks which will be useful to them, if they repeat the following experiments, or make new ones. We should give the preference to double microscopes, in which we see objects perpendicularly, from their having a plain or concave mirror, which shews the objects clear; the concave mirror is the most preferable when the observations are made with the strongest lens. Leeuwenhoek, who undoubtedly has been the greatest and most indefatigable of all microscopical observators, is said to have only made use of simple microscopes, with which he viewed objects horizontally. If this is true, it is necessary to remark, that most of the plates given by Leeuwenhoek of microscopical objects, especially spermatic animals, represents them much thicker and longer than he really saw them, which renders the microscopes we speak of preferable to the horizontal, as they are more stable; the motion of the hand, with which the microscope is held, producing a little trembling, which causes the object to appear wavering, and never presents the same part for any time. Besides, there is always a motion in the liquors caused by the agitation of the external air, at least, if we do not put the liquor between two plates of glass, or even fine talc, which diminishes somewhat of its transparency, and greatly lengthens the experiment; but the horizontal microscope, whose tables are vertical, has the still greater inconvenience, that the most ponderous parts of the drop of liquor fall to the bottom; consequently there are three motions, that of the trembling of the hand, the agitation of the fluid by the action of the air, and also that of the parts of the liquor falling to the bottom: from the combination of which, certain small globules, which we see in these liquors, may appear to move by their own motion and powers, while they only obey the compounded power of those three causes.

When we put a drop of liquor on the table of the double microscope, although horizontally placed, and in the most advantageous situation, we still see one common motion in the liquor, which forces all what it contains to one side. We must wait till the fluid is in an equilibrium and at rest, before we make our observations; for it often occurs, that this motion of the fluid hurries away many globules, and forms a kind of whirling motion, which returns one of these globules in a very different direction to the others. The eye is then fixed on the globules, and seeing one take a different course from the rest, supposes it an animal, or at least a body, which moves of itself, whereas its motion is only owing to that of the fluid; and as the liquor is apt to dry and thicken in the circumference of the drop, endeavours must be made to fix the lens on the centre of it. The drop should also be as large as possible, and contain as much liquor as will permit a sufficient transparency, to see perfectly what it contains.

Before we begin to make observations, we should have a perfect knowledge of our microscope. There is no glass whatsoever but in which there are some spots, bubbles, threads, and other defects, which should be nicely inspected, in order that such appearances should not be represented as real and unknown objects: we must also endeavour to learn what effect the imperceptible dust has which adheres to the glasses of the microscope; a perfect knowledge of which may be acquired by observing the microscope several times.

To make proper observations, the sight, or focus, of the microscope must not precisely fall on the surface of the liquor, but a little above it; as not so much reliance should be placed on what passes upon the surface, as what is seen in the body of the liquor. There are often bubbles on the surface which have irregular motions produced by the contact of the air.

We can see much better with the light of two short candles, than in the brightest day, provided this light is not agitated, which is avoided by putting a small shade on the table, inclosing the three sides of the lights and the microscope.

It will often appear as though dark and opaque bodies become transparent, and even take different colours, or form concentrical and coloured rings, or a kind of rainbow on the surface; and other matters, which are seen at first sight transparent and clouded, become black and obscure; these changes are not real, but only depend on the obliquity the sight falls on the body with, and the height of the plain in which they are found.

When there are bodies in a liquor which seem to move with great swiftness, especially when they are on the surface, they form a furrowed motion in the liquor, which appears to follow the moving body, and which we might be inclined to mistake for a tail. This appearance deceived me at first, but I clearly perceived my error, when these little bodies met others which stopped them; for there was no longer any appearance of tails. These are the remarks which occurred during my experiments, and which I submit to those who would make use of the microscope for the observation of liquors.

PLATE I.

EXPERIMENTS.

I. I took from the seminal vessels of a man, who died a violent death, and whose body was still warm, all the liquor therein contained, and put it into a small bottle; of this I put a drop on the table of the microscope, without the addition of water or any other liquor. The first thing which presented, was a vapour which steamed from the liquor towards the lens, and obscured it. These vapours being dissipated, I perceived large filaments, ([fig. 1.]) which in some places seemed to extend into different branches, and in others to intermingle together. These filaments clearly appeared to be internally agitated by an undulating motion, and looked like hollow tubes which contained some moving substance. I distinctly saw two of these filaments ([fig. 2.]) were joined together, and had a vibration nearly like that of two extended strings, which are tied at the two extremities, and pulled asunder in the middle. These filaments were composed of globules which touched each other, and resembled beads. I afterwards saw filaments which swelled in certain parts, and I observed, that on the side so swelled small globules came out, which had a distinct motion like that of a pendulum; these small bodies were fastened to the filaments by a small thread, ([fig. 3.]) which lengthened gradually as the little body moved; and at last I saw these little bodies entirely separated from the large filament, carrying after them the small thread which connected them. As this liquor was very thick, and the filaments too near each other, I dilated another drop with rain water, in which I was assured there were no animals. I then saw the filaments much separated, and very distinctly perceived the motion of these little bodies, which was now more free, and they swam much quicker; and if I had not seen them separate from the filaments, and carry along with them their thread, I should have taken the moving body in this second observation for an animal, and the thread for its tail. I then attentively observed one of these filaments, that was much thicker than these small bodies, and I had the satisfaction of seeing two of those bodies which separated with difficulty, drag along with them a long and small thread, which obstructed their motion.

This seminal liquor was at first very thick, but by degrees it became more fluid; in less than an hour it was almost transparent; and in proportion as this fluidity increased, the phenomena changed, as I shall relate.

II. When the seminal liquor attained more fluidity, the filaments were no longer to be seen, but the little bodies appeared in great numbers; they have for the most part a motion like that of a pendulum, and they draw after them a long thread, which it may clearly be perceived they want to get rid of; their motion forwards is very slow, vibrating to the right and left. The motion of a boat fastened in the midst of a rapid stream to one fixed point, pretty well represents the motion of these bodies, excepting that the boat remains in the same place, whereas they advance by degrees; but they do not always keep the same parts in the same direction; but at each vibration they take a considerable rolling motion; so that, besides their horizontal motion, they have one of a vertical balance, which proves that these bodies are of a globular figure, or, at least, that their lowest part is not sufficiently extended to maintain them in the same position.

III. At the end of two or three hours, when the liquor was more fluid, we saw a greater quantity of these moving bodies. They seemed to be more free; the threads were shorter; their progressive motion was more direct, and their horizontal motion was greatly diminished; for the longer the threads are, the greater is the angle of their vibration; and in proportion as these threads diminish in length, the vibratory motion lessens, and the progressive motion increases. The vertical balance still subsisted, and was always plainly perceptible.

IV. In five or six hours the liquor attained its utmost fluidity. Most of these moving substances were entirely disengaged from their threads; they were of an oval figure, ([fig. 4.]) and moved progressively with great swiftness, and by their various motions had a stronger resemblance than ever to real animals. Those who had their threads still adhering, were not so brisk as the others; and among these that had not threads, some seemed to change their shape and size, some were round, some oval, and others thicker at their extremities than in the middle; the balancing and rolling motion was still observable.

V. At the end of twelve hours a kind of gelatinous matter was settled at the bottom of the bottle: it was of an ash-colour, and of a tolerable consistency; the liquor that swam above was almost as clear as water, with a kind of bluish tint, resembling water in which a little soap had been dissolved; nevertheless it still preserved its viscidity. The moving bodies had then a great activity, were loosened from their threads, and moved in all directions. I saw some of them change their form, and from oval become round; and others separate, and from one oval form two. As they became smaller, their activity increased.

VI. In twenty-four hours the liquor had deposited a greater quantity of gelatinous matter. I diluted it with water, but it did not readily mix, and required a considerable time to dissolve. It then appeared composed of an infinite number of opaque tubes that formed a kind of net-work, in which no regular disposition nor the least motion could be seen: in the clear liquor some few small bodies were still moving. The next morning there were also a very few; but after that time I saw no more in this liquor than in the globules, without any appearance of motion.

These experiments were repeated several times with the most possible exactness; and I am persuaded that those threads above mentioned are not tails, nor do they make any part of the individual body; for these threads have no proportion with the rest of the body; they are of different sizes, although the moving bodies are always nearly of the same, at the same time. The globule appears embarrassed in its motion, as its tail is longer or shorter; sometimes it cannot advance, but move only from right to left, or from left to right, when the tail is very long; and it is clearly seen that they use great efforts to get rid of them.

VII. Having taken the seminal liquor from another man but just dead, and still warm, I put a drop of it on the table of the microscope, and it immediately liquified; it had at first a condensed appearance, and seemed to form a compact web, composed of long and thick filaments, which grew from the thickest part of the liquor. These filaments separated in proportion as the liquor became more fluid, and at length they divided into globules, which at first seemed not to have sufficient power to set themselves in motion, but this power increased as they separated from the filament, from which they made many efforts to disengage themselves. Each of them in this struggle drew out tails from the filaments of different sizes, some of which were so thin and so long as to have no proportion with the bodies, which were all so much the more embarrassed as these threads or tails increased in length. The angle of their vibratory motion was also much greater as those filaments were longer: and their progressive motion so much the more remarkable as these tails were shorter.

VIII. Having continued these observations for fourteen hours, I perceived that these threads, or tails, were continually lessening, and became so fine, that at last their extremities were no longer visible, and at length the whole entirely disappeared. At this time the globules absolutely ceased their horizontal vibrations; their progressive motion was direct, although they had always the vertical balancing motion, like the rolling of a ship. When disencumbered of these threads, the bodies were oval, transparent, and perfectly like those pretended animals seen in the liquor of an oyster on the seventh day, and still more to those found in the jelly of roast veal at the end of the fourth day.

IX. Between the tenth and eleventh hour the liquor became extremely fluid, and all the globules appeared to proceed in ranks from one and the same side; ([fig. 5.]) they passed over the table of the microscope in less than four seconds; they were ranged seven or eight in front, and moved on successively, as troops march in files. I observed this singular instance for more than five minutes; and as their course did not finish, I was desirous of finding the source: and, having gently moved my glass, I perceived that all these moving globules came from a kind of mucilage, ([fig. 6.]) where the filamentary net-work continually produced them more abundant and much quicker than the filaments had ten hours before. There was still a remarkable difference between these moving bodies produced in the thick liquor, and those produced when the liquor became more fluid; these last had no thread behind them, their motion was quicker, and they went in flocks like sheep. I observed the mucilage from whence they issued for some time, and perceived it diminished, and was successively converted into moving globules, till the diminution of more than half the bulk; after which, the liquor being too dry, this mucilage became obscure in its middle, and all the environs were divided by the small threads which appeared to be formed from the bodies of these moving globules which were destroyed as it dried up, not in one single mass, but in long threads, regularly disposed, with quadrangular intervals, forming a net-work, very like to a cobweb, on which the moisture hung in an infinite number of globules.

X. I perceived by the first experiment, that these little moving bodies change their form, and I thought they in general diminished, but of that I was not certain. In this last observation, at the twelfth and thirteenth hour I observed it more distinctly; at the same time remarking that though diminished considerably in size, yet they increased in specific gravity; especially when their motion was nearly finished, which generally happened all at once and they sunk to the bottom, forming a sediment of an ash-colour, plainly perceptible to the naked eye, and which appeared through the microscope to be composed of globules adherent to on another, sometimes by threads, and at others in knots, but always in a regular manner.

XI. Having procured the seed of a dog, emitted naturally, I observed that this liquor was clear, and had but little tenacity. I put it in a phial, and having examined it with a microscope, without diluting it with water, I perceived moving bodies entirely like those I had observed in the human semen; they had threads, or tails, perfectly the same; they were also nearly of the same size; in a word, they resembled, as perfectly as possible, those I saw in the human liquor, liquified during two or three hours. I then sought for the filaments which I had seen in the human liquor, but it was useless; I perceived only some long threads entirely like those which served as tails to the globules. These threads were not attached to any globules, nor had they any motion. Those globules which were in motion, and had tails, appeared to me to move quicker than those in the human semen: they had scarcely any horizontal vibrations, but a rolling motion. They were not in a great number; and, although their progressive motion was stronger, they took more time to cross the microscope than those I had before remarked. I observed this liquor for three hours, but perceived no change: after which I examined it at another time for four hours, and remarked, that the number of moving bodies diminished by degrees; the fourth day there was still some, though they were very few, and often I only found one or two in a drop of liquor. The second day most of them were deprived of their tails; the third day very few retained them, yet, at the last day, there still remained some which had them; the liquor had then deposited a whitish sediment, which appeared to be composed of immoveable globules, and many threads, that seemed to be tails separated from the globules. There were also some attached to the globules, which appeared to be the dead bodies of these little animals, but whose forms were different from those that moved, for they appeared larger than the moving globules, or the rest, which remained without motion at the bottom of the liquor, and appeared to have a fissure or opening.

XII. Another time, having taken the seminal liquor of the same dog, I again perceived the fore-mentioned phenomena; and I saw, besides, in one of the drops of this liquor, a mucilaginous part, which produced moving globules, as in the ninth experiment, ([fig. 6.]) and these globules formed a current, and went in ranks like troops. This mucilage appeared to me animated with an internal inflated motion, which produced small bloated appearances in different parts, and from whence issued these bloated forms, or moving globules, with a nearly-equal swiftness, and in the same direction. The bodies of these globules were not different from the rest, excepting they had no tails. I observed that many of them changed their shape, and lengthened considerably, till they became little cylinders, after which the two extremities of the cylinders were bloated, and divided into two globules, both moving and following the same direction as that before they were united.

XIII. The phial, which contained this liquor, having been broke by accident, I, a third time, took the liquor of the same dog, but whether the animal was wearied by too reiterated emissions, or by other causes, the seminal liquor contained none of the above bodies, but was transparent and viscous, like the serum of blood; I examined it then, and at one, two, three, and even twenty-four hours afterwards, but it presented nothing new: there was not a single moving body to be seen, nor any mucilage; in a word, nothing that I had seen before.

XIV. I then opened a dog, and separated the testicles and the adherent vessels, but I perceived no seminal vesicles, and apparently the seed in those animals passes directly from the testicles into the urethra. I found but a small quantity of liquor in the testicles, although the dog was adult and vigorous. In the small quantity I could collect I could not discover any bodies that were in motion. I only perceived a great quantity of very small globules, most of which were motionless, and some of the smallest had some trifling approximating motion, which I could not follow, because the drops I gathered were so exceedingly minute that they dried in two or three minutes after they were placed in the microscope.

XV. Having cut the testicles of this dog into two parts, I infused it in water, and closely sealed up the vessel. Three days after I examined this infusion, which I made with the design of discovering whether the flesh did not contain moving bodies, and I saw a great quantity of moving bodies of a globular and oval form, like those I had seen in the seminal liquor of the dog, excepting they had not any threads. They moved in all manner of directions with great swiftness. I observed these bodies, which appeared animated for some time, and saw many change their form; I perceived some to lengthen, and others to contract, while some swelled at both extremities: there were numbers that were smaller and thicker than the rest; but they were all in motion, and were about the size and figure of those I have described in the fourth experiment.

XVI. The next morning the number of these globules were increased, but they appeared smaller; their motion was more rapid and irregular; they had also another appearance with respect to their form and manner of moving, which seemed confused; the next and several days after, till the fifteenth day, there were moving bodies in the water, whose size gradually diminished till they were no Longer visible. The last, which I perceived with great difficulty, was on the nineteenth and twentieth days, and they moved with greater rapidity than ever. Upon the water a kind of pellicle was formed, which appeared to be composed of the coverings of those moving bodies, small threads, scales, &c. but entirely motionless; this pellicle, and the moving bodies could not come into the liquor by means of external air, since the bottle had been kept carefully sealed.

XVII. I then successively opened ten rabbits, on different days, to examine their seminal liquors; the first had not a drop, either in the testicles or seminal vessels. In the second I was no more successful, although I was assured he was the father of a very numerous progeny. I succeeded no better in the third. I then imagined that the presence of the female might be requisite; I therefore put males and females into cages so contrived that it was impossible for them to copulate. At first these endeavours did not succeed; for, on opening two, not a drop of seminal liquor was to be found; however, in the sixth that I opened, a large white rabbit, I found, in the seminal vesicles, as much liquor as could be contained in a teaspoon; this matter resembled calves' jelly, was nearly transparent, and of a citron colour. Having examined it with the microscope, I perceived it to resolve, by slow degrees, into filaments and thick globules, many of which appeared fastened to each other; but I did not remark any distinct motion in them, only as the matter liquefied, it formed a kind of current by which these filaments and globules seemed to be drawn all to one side. I expected to find this matter take a greater degree of fluidity, but that did not happen, for, after it was a little liquefied, it dried, and I could perceive nothing further than what is above mentioned. When this matter was mixed with water, the latter did not appear to have power to dilute it.

XVIII. Having opened another rabbit, I only found a very small quantity of seminal matter, which was of a colour and consistency entirely different from the former; it was scarcely tinctured of a yellow hue, and was much more fluid. As there was but very little, I feared it would dry too hastily, and therefore mixed it with water: from the first observation, I did not perceive the filaments I had seen in the other, but I discovered three globules, all in a trembling and restless motion; they had also a progressive motion, but it was very slow; some moved round the others, and most appeared to turn upon their centres. I could not pursue this observation because the liquor so soon got dry.

XIX. I opened another of these rabbits, but could not discover any of this matter; in the seminal vessels of another, I found almost as much congealed liquor as in [XVII]th Experiment: I examined it in the same manner as the rest, but it afforded me no greater discovery. I infused the whole I had collected, in almost double the quantity of water, and after briskly shaking them together, I suffered them to settle for ten minutes; after which, on inspecting this infusion, I saw the same large globules as before; there were but few and those very distant from each other. They had approximating motions with respect to each other, but they were so slow, as to be scarcely discernable; two or three hours after, these globules seemed to be diminished, their motion was become more distinct, and they appeared to turn upon their centres. Although this trembling motion was more than their progressive, nevertheless they were clearly seen to change their situation irregularly with respect to each other. Six or seven hours after the globules were become still less, and their action was increased: they appeared to me to be in much greater numbers, and all their motions distinct. The next morning, there was a prodigious multitude of globules in motion, which were at least three times smaller than those that at first appeared. I observed these globules for eight days, and observed that many of them seemed to join together, after which their motion ceased; this union, however, appeared to me only superficial and accidental. Some were larger than others; most were round and spherical, and some of them were oval. The largest were most transparent, and the smallest were almost black. This difference did not proceed from the light, for in whatever situation these small globules were in, they were always of the same appearance; the motions of the small were much more rapid than the large ones, and what I remarked most clearly and most generally in all, was their diminution of size, so that at the eighth day they were so exceedingly small as to be hardly perceptible, and at last absolutely disappeared.

XX. At length having obtained, with no small difficulty, the seminal liquor of another rabbit, as it would have been conveyed to the female, I remarked it to be more fluid than that which had been taken from the seminal vesicles, and the phenomena which it offered were also very indifferent; for in this liquor there were moving globules and filaments without motion; and also a kind of globules with threads or tails, resembling those of a dog or a man, but only appearing smaller and brisker ([fig. 7.]) They passed over the microscope in an instant, their tails appeared shorter than those of other spermatic animals, and I own I am not certain whether some of those tails were not false appearances, produced by the furrows which these moving globules formed in the liquor, as they moved with too great a rapidity to admit of my clearly observing them; besides, the liquor, though sufficiently fluid at first, very speedily dried away.

XXI. After this I resolved to examine the seminal liquor of a ram; I applied to a butcher, who supplied me with the necessary parts of at least twelve or thirteen, directly after they were killed, but I could not find liquor sufficient for any experiment, either in the epididymis or seminal vesicles. In the little drops I was able to collect, I only perceived globules which had no motion. As I made these experiments in March, I supposed by repeating them in October, the season of female attachments, I should discover more seminal liquor in these vessels. I cut many of these testicles in two longitudinally, and collected a small quantity of liquor, but found nothing more in them.

PLATE. II.

XXII. I took three of these testicles, of three different rams, cut each of them into four parts, and put them into separate bottles, with as much water as was sufficient for them. Securing these bottles from the admission of air I suffered the infusion to remain for four days, after which I examined the liquor of each by the microscope, and found them all replete with an infinity of moving bodies, most part of which were oval, and the rest globular; they were pretty thick, and resembled those described in the [VIII]th experiment; their motion was neither brisk, uncertain, nor very rapid, but equal, uniform, and in all directions. These moving bodies were nearly of the same size in each liquor, but differed one bottle with the other. They had no tails, nor were there any filaments or threads in this liquor; during the fifteen or sixteen days they were retained, they often changed their form, and seemed successively to throw off their external coverings; they also became every day smaller, and on the sixteenth day, they were no longer perceptible.

XXIII. In the month of October I opened a ram, and found a great quantity of seminal liquor in the epididymis; having examined it with the microscope, I perceived an innumerable multitude of moving bodies, so numerous, that all the liquor seemed to be entirely composed of them; as it was too thick, I diluted it with water, but I was surprised to see the motion of these bodies suddenly stop, though I perceived them very distinctly; having many times repeated the same observation, I perceived that the water which diluted the seminal liquors of a man, a dog, &c. seemed to coagulate that of a ram.

XXIV. I then opened another ram, and in order to prevent the seminal liquor from coagulating, I permitted the parts of generation to remain in the body of the animal, and covered it over with warm clothes. By these precautions I observed the seminal liquor in its fluid state; it was replete with an infinity of oblong moving bodies, ([fig. 8.]) traversing in various directions; but as soon as the liquor grew cold, the motion of all these bodies immediately ceased. I diluted the liquor with warm water, when the motion of the small bodies remained for three or four minutes. The quantity of these moving bodies was so great in this liquor, that although diluted, they nearly touched each other. They were all of the same size and form, but none of them had tails. Their motion was not very quick, and when it stopped by the coagulation of the liquor, they did not change their form.

XXV. As I was persuaded, not only by my own theory, but also by the observations of all those who had made experiments before me, that the female, as well as the male, has a seminal and prolific liquor; and, as I had no doubt, but the reservoir of this liquor was the glandular body of the testicle, where prejudiced anatomists attempted to find the egg, I purchased several dogs and bitches, and some male and female rabbits, which I kept separate from each other; and in order to have a comparative object with the liquor of the female, I again observed the seminal liquor of a dog, and discovered there the same moving bodies as described in the [XI]th experiment.

XXVI. While I was thus occupied, a bitch was dissected which had been four or five days in heat, and had not received the dog. The testicles were readily found, and on one of them I discovered a red, glandular, prominent body, about the size of a pea, which perfectly resembled a little nipple; on the outside was a visible orifice formed by two lips; one of which jutted out more than the other. Having introduced a small instrument into this orifice, a liquor dropped from it, which we carefully caught to examine with the microscope. The surgeon replaced the testicles in the body of the animal, which was yet alive, in order to keep them warm. I then examined this liquor with a microscope, and, at the first glance, had the satisfaction to see moving bodies with tails, exactly like those I just before saw in the seminal liquor of the dog. ([fig. 9.]) Messrs. Needham and Daubenton, who observed them with me, were so surprized at this resemblance, that they could scarcely believe but that these spermatic animals were the same, and thought I had forgotten to change the table of the microscope, or that the instrument with which we had gathered the liquor of the female, might before have been used for the dog. Mr. Needham then took different instruments, and having obtained some fresh liquor, he examined it first, and saw there the same kind of animals, and was convinced, not only of the existence of spermatic animals in the seminal liquor of the female, but likewise of their resemblance to those of the semen of the male. We repeated it ten times at least, in different drops of the same liquor, without perceiving the smallest variation in the phenomena.

XXVII. Having afterwards examined the other testicle, I found a glandular body in its growing state; it had not any external orifice, was much smaller, and not so red as the first. Having opened it, I found no liquor; but only a small fold in the internal part, which I judged to be the origin of the cavity that was to contain the liquor. This second vesicle had some very small lymphatic vesicles externally. I pierced one of them with a lancet, and a clear and limpid liquor flowed out, which I examined with the microscope; it contained nothing similar to that of the glandular body; it was a clear matter, composed of small globules, which were motionless. Having often repeated this observation, I was assured, that this liquor in the vesicles was only a kind of lymph, which contains nothing animated, or similar to that seen in the female seed, which is formed and perfected in the glandular bodies.

XXVIII. Fifteen days after I opened another bitch that had been in heat seven or eight days, but had not received the dog. I found the testicles contiguous to the extremities of the horns of the matrix; these horns were very long, their external tunic surrounded the testicles, and they appeared covered with that membrane like a cowl. In each testicle I found a glandular body in its full maturity. The first was half open, and there was a passage which penetrated into the testicle, and which was replete with seminal liquor; the second was somewhat more large and prominent, and the orifice, or canal, which contained the liquor was below the nipple. I took these two liquors, and having compared them, found them perfectly alike. The seminal liquor of the female is at least as liquid as that of the male. Having afterwards examined the two liquors with the microscope, I perceived the like moving bodies, ([fig. 10.]) and the same phenomena, as in the seminal liquor of the other. I saw besides many globules which moved very briskly, and endeavoured to disengage themselves from the mucilage that surrounded them: there was a great quantity of them as in the seed of the female.

XXIX. From these glandular bodies I pressed out all the liquor, and having collected it, I found enough to last for four or five hours observations. I remarked that it deposited somewhat to the bottom, or at least began to thicken. I took one drop of this, which was thicker than the rest, and having put it on the microscope, perceived that the mucilaginous part of the seed was condensed, and formed a continued net-work. On the external border of this net-work, there was a torrent, or current, composed of globules, which moved with rapidity. These globules were lively, active, and appeared to be disengaged from their mucilaginous covering, and their tails. This stream perfectly resembled the course of the blood in small transparent veins; for they appeared not only to be animated by their own powers, but also to be impelled by a common force, and constrained to follow in a herd. From this experiment, and the [XI]th and [XII]th, I concluded, that when the fluid begins to coagulate and thicken, these active globules break and tear their mucilaginous coverings, and escape by that side where the liquor remains most fluid. These moving bodies had then neither threads nor tails; they were for the most part oval, and appeared to be flat at the bottom, for they had no rolling motion.

XXX. The horns of the matrix were externally soft; I opened them longitudinally, and only found a very small quantity of liquor, which, upon examination, appeared to contain the same as that pressed from the glandular substance of the testicle. These glandular bodies are placed so as easily to sprinkle this liquor on the horns of the matrix; and I am persuaded that, as long as the amorous season remains, there is a continual dropping of this liquor from the glandular substance into the horns of the matrix; that this dropping remains till the glandular substance has emptied the vesicles; it then becomes fluid by degrees, is effaced, and only leaves a little reddish cicatrice on the external part of the testicle.

XXXI. I took this seminal liquor of the female, with the same quantity of that just emitted from the male, and mixed them together, and having examined this mixture with the microscope, I perceived nothing new, the liquor remaining the same, and the moving bodies were so similar, that it was impossible to distinguish those of the male from those of the female; I only thought their motion appeared a little slackened.

XXXII. Having dissected a young bitch that had never been in heat, I only discovered a small protuberance on one of the testicles, which I supposed to be the origin of a glandular body. The surface of the testicles was smooth and even, and the lymphatic vessels could scarcely be seen externally, until the tunic, which covered the testicles, was separated; but these vesicles were not considerable, and contained but a small quantity of liquor, in which I could only perceive some little globules without any motion.

XXXIII. In another bitch, which was younger, and only three or four months old, there was no appearance of glandular bodies on the testicles; they were white, smooth, and covered with a cowl like the rest. There were some little vesicles which contained little or no liquor; and it was with great difficulty we could perceive any vesicles externally. I compared one of these testicles with that of a young dog of nearly the same age, and they appeared internally of a fleshy nature, and perfectly similar. I do not mean to contradict what some anatomists have said concerning the testicles of dogs, but only that the appearance of the internal substance of the female testicles is like that of the males, when the glandular substances are not yet grown.

XXXIV. The genital parts of a cow, which had been just killed, was sent to me, covered over with hot cloths, and put into a basket with a live rabbit, which likewise squatted on a cloth at the bottom, so that I received them almost as warm as when taken out of the body. I immediately inspected the testicles, and found them of the size of a hen's, or, at least, a pigeon's egg. One of these testicles had a glandular body, about the size of a pea, protuberating outwardly like a small nipple, but it was not pierced, nor had any external orifice: it was close and hard. I pressed it with my fingers, but no liquor issued from it. I observed, before this testicle was dissected, there were two other glandular substances at a distance from the other; but these were just begun to grow; their colour was a whitish yellow, whereas that which seemed to have pierced the membrane of the testicle was of a rose colour. I opened this last, and examined it with the greatest attention, but could not discover that it contained any liquor, I therefore judged that it was far distant from its maturity.

XXXV. The other testicle had no glandular body which had pierced the common membrane that covered the testicle, there were only two small ones, which began to form a little protuberance below this membrane. I opened both of them but no liquor issued therefrom: they were hard, whitish, and with a little yellow tint; each of them had four or five lymphatic vesicles, very easily distinguishable on their surface, and appearing transparent. I judged they contained a quantity of liquor, and having pierced them with a lancet, the liquor issued out to some inches distance. I collected a sufficient quantity of this liquor to observe it easily; I only saw some very minute immoveable globules; and although I continued my examination for two days, I neither discovered alteration, change, nor motion, therein.

XXXVI. Eight days after, two more genital parts were brought to me in the same mode as the last. I was assured that one was taken from a young cow that had never calved, and the other from one that had had several, but was not old. I first examined the testicles of the latter, and on one of them I found a glandular substance, as large and as red as a cherry, which appeared a little soft towards the nipple. I distinguished three small holes, in which a hair might be introduced. Having pressed this substance with my fingers a small quantify of liquor issued, which I placed on the table of a microscope, and had the satisfaction to see some moving globules there, but quite different from those which I had seen in other seminal liquors ([fig. 11.]). These globules were obscure and little; their progressive motion, although distinct, was, nevertheless, very slow. The liquor was not thick; the little globules had no appearance of threads, or tails, and they were not all in motion. This is all I was able to perceive in the liquor this glandular substance afforded me, for although I pressed it again, it only afforded a less quantity, mixed with blood. I again discovered it in the small moving globules, but they seemed to be at least four times smaller than the sanguinary globules.

XXXVII. This glandular body was situate at one of the extremities by the side of the horn of the matrix, and the liquor, which it prepares, must fall upon this horn; nevertheless, on opening this horn I found no material quantity of liquor. This glandular body penetrated very forward in the testicle, and occupied more than a third of its internal substance. I opened them longitudinally, and found a pretty large cavity, but entirely void of any liquor. At some distance from this glandular body there was a small one of the same kind, about the size of a lentil. There were also two small cicatrices, about the same size, which formed two small indentations, of a deep red colour: they were the remains of obliterated glandular bodies. Having afterwards examined the other testicle, I counted four cicatrices and three glandular bodies; the foremost of which had pierced the membrane, was of a flesh colour, and the size of a pea. It was solid, and without any orifice or liquor: the two others were smaller, harder, and of a deep orange colour. On the first testicle only two or three apparent lymphatic vesicles remained. I counted eight on the external part, and having examined the liquor of these vesicles I perceived only a transparent matter, without any moving bodies.

XXXVIII. I then examined the testicles of the young cow which had not calved, which, notwithstanding, were something larger than the other, but it is true there were no cicatrices on either of them; the one was smooth and very white, and a number of lymphatic vesicles were sprinkled about it, but there was not the least mark of a glandular body. On the other testicle I perceived the marks of two glandular substances, the one had just began to grow, and the other was the size of a pea; there was also a great number of lymphatic vesicles, which I pierced with a lancet, but the liquor did not contain any thing; having pierced the two small glandular bodies some blood alone issued thereout.

XXXIX. I divided each testicle of both cows into four parts, and, having put them into separate phials, I poured as much water on as would cover them, and after having closely corked them up, I suffered to infuse for six days; I then examined these infusions, and discovered an innumerable quantity of living moving bodies ([fig. 12.]); they were all, in these infusions, extremely small, moved with a surprising rapidity in all directions. I observed them for three days, and they always appeared to diminish, till at last, on the third day, they entirely disappeared.

XL. The following day they brought to me the genital parts of three more cows. I immediately searched the testicles to find one where the glandular substance was in perfect maturity; but in two of them I only discovered some growing glandular substances on the testicles. I could not learn whether these cows had calved or not, but there was a great appearance they had all been in season, for there were a great number of cicatrices on all these testicles. In the third I found a testicle, on which was a glandular substance, as thick and as red as a cherry; it was inflamed, and seemed to be in full maturity. Its extremity was a nipple, with a small hole; I pressed it a little between my fingers, and a quantity of liquor issued out. I found in this liquor moving globules, exactly like those in the liquor pressed from the glandular body of the other cow, I have before spoken of in experiment [XXXVI]. They appeared to be more numerous, their progressive motions were not so slow, and their size larger. Having observed them for some time I perceived some to lengthen and change their form. I then introduced a very fine instrument into the little hole of the glandular substance, and having opened it I found the internal cavity replete with liquor; this liquor offered me the same phenomena, and the same moving globules, as I before observed in experiment [XXXVI]. with either filaments, threads, or tails attached to them. The liquor of the vesicle presented me with nothing more than nearly a transparent matter, which did not contain one moving thing.

XLI. At different times they brought me the genitals of several other cows. In some I found the testicles loaded with an almost mature glandular substance; in others they were of different growths, and I remarked nothing new, excepting that in the two testicles of two different cows I perceived the glandular substance in a decayed state; the base of one was as broad as the circumference of a cherry; the extremity of the nipple was soft, wrinkled, and shrivelled; the two small holes were very perceptible, from whence the liquor had flowed. With some difficulty I introduced a small hair, but there was no liquor in the canal, nor in the internal cavity, which was still to be seen. The flaccidity of these glandular substances begins, therefore, at the most external part, or extremity of the nipple. They diminish at first in height, and afterwards in breadth, as I observed in another testicle, where this glandular substance had diminished more than three fourths.

XLII. As the testicles of doe rabbits, as well as the glandular bodies formed there, are very small, I could observe nothing very exactly with respect to their seminal liquor. I only discovered, that the testicles of doe rabbits are different, and that none of those I saw resembled what De Graaf represents in his engravings; for the glandular substances did not enclose the lymphatic vesicles; and I never saw a pointed end, as he has depicted them.

XLIII. I found on the testicles of some cows a kind of bladders, replete with transparent liquor. I remarked they were of different sizes, the largest about that of a pea; they were fastened to the external membrane of the testicle by a strong membraneous pedicle, as was also another, still smaller; and a third, nearly of the same size as the second, appeared to be only a lymphatic vesicle, much more apparent than the rest. I imagined these bladders, which the anatomists have called hydatides, might possibly be of the same nature as the lymphatic vesicles of the testicles, for having examined the liquor they contained I found it to be perfectly similar; it was a transparent and homogeneous liquor, which did not contain one moving substance.

XLIV. At the same time I made observations on the liquor in an oyster; on the water in which pepper had been boiled; on the water wherein pepper had been only infused; and on the water wherein I had put some vegetable seed; the bottles which contained these waters were firmly closed, and in two days I perceived in the oyster liquor a great quantity of oval and globular substances, which seemed to swim like fish in a pond, and had all the appearance of being animals; however they had no limbs nor tails, but were very large, transparent, and visible. I perceived them change their forms, and become smaller for seven or eight days successively; and at length I and Mr. Needham observed animals similar to those in an infusion of jelly of roast veal, which had been also very exactly corked; so that I am persuaded they are not real animals, at least according to the received acceptation of the words, as we shall hereafter explain.

The infusion of the seed presented an innumerable multitude of moving globules which appeared animated like those of the seminal liquors, and in the infusions of the flesh of animals: these were also large, and in violent motion during the first days, but they diminished by degrees, and disappeared only from their minuteness.

I perceived the same thing, but later, in the liquor wherein pepper had been boiled, and the like, though still later, in that which had not boiled; from hence I supposed that what is called fermentation may possibly be only the effect of the motion of these organical parts of animals and vegetables; and in order to see what difference there was between this kind of fermentation and that of minerals, I placed a little powdered stone on the microscope, and sprinkled thereon a drop of aquafortis, which however produced a different phenomena, consisting of great balls, which ascended to the surface, and almost instantaneously obscured the focus of the microscope: this was a dissolution of the grosser parts, which being completed it became motionless, and had not the smallest resemblance to the other infusions I had observed.

XLV. I examined the seminal liquor in the roes of different fish; such as carp, tench, barbel, &c. which I took out while they were living, and having observed three different liquors with great attention, I perceived a great quantity of obscure globules, all in motion. I took several more of these fish alive, and with my fingers gently compressed that part of the belly where this liquor is emitted; and in that which I obtained, I perceived an infinity of moving globules therein, very black and very small.

XLVI. Before I finish this chapter I shall relate the experiments of Mr. Needham on the seed of a kind of cuttle fish, called calmar. This able naturalist having sought for spermatic animals in the milts of many different fish, found them in the roe of a calmar, apparent to the naked eye. During the summer he dissected calmars at Lisbon, but found no appearance of any roe, nor any reservoir which appeared to be destined for the reception of the seminal liquor; and it was in the middle of December that he began to discern the first traces of a new vessel replete with a milky juice. This reservoir increased, and the seed which it contained was diffused very abundantly. By examining this liquor with the microscope, he perceived only small opaque globules, which floated in a kind of serous matter, without the least appearance of life. But some time after, in the milt of another calmar, he found these organic parts completely formed; they seemed like spiral springs shut up in a kind of transparent case. They appeared as perfect at first as they did at last, excepting that by degrees they contracted and formed a kind of screw. The lid of the case was a species of valve that opened outwardly, and by which all the contents might issue; it contained another valve, a barrel, and a spongy substance; therefore the whole machine consisted in an external, transparent, and cartilaginous case, whose upper extremity is terminated by a round head, formed by the case itself, and which performs the office of a valve. In this external case is contained a transparent tube, which encloses the spring, piston, or valve, barrel, or spongy substance. The screw occupies the upper part of the tube and case, the piston and barrel are placed in the middle, and the spongy substance occupies the lower part. These machines pump up the lacteal liquor, of which the spongy substance is full; and before the animal spawns, the whole milt is no more than a composition of these organic parts, which have absolutely pumped up the lacteal liquor. As soon as these little machines are taken from the body of the animal, and deposited either in water, or held in the air, they begin to act; the spring ascends, followed by the piston, the barrel, and the spongy substance which contains the liquor; and as soon as the spring and the tube which contain it begin to quit the case, the spring folds up; and all that remains within begins to move, till the spring, the sucker, &c. are entirely come out: as soon as that is done, the remainder immediately follow, and the lacteal liquor, which has been pumped out, and which was contained in the spongy substance flows out by the barrel.

As this observation is very singular, and incontestibly proves that the moving bodies found in the milt of the calmar are not animals, but simple machines, a kind of pumps, I have deemed it necessary to give Mr. Needham's own words.[Q]

[Q] See New Discoveries made with the microscope by Mr. Needham, chap. vi. Leyden, 1747.

"When the small machines, he says, are arrived to their perfect maturity, many of them act the moment they are in the open air; nevertheless most of them may be commodiously placed, so as to be seen with a microscope, before their action begins; and even to make them act, the upper extremity of the external case must be moistened with a drop of water which then begins to expand, while the two small ligaments which issue from the case twist and turn in different manners: at the same time, the screw ascends slowly, the volutes, which are at its upper end, approach and act against the top of the case: those at the bottom also advance, and seem to be continually followed by others which come from the piston. I say, they seem to be followed, because I do not think they are so effectually, but only a deception produced by the nature and motion of the screw. The piston and barrel also follow the same direction, extend lengthways, and at the same time move towards the top of the case, which is perceived by the vacuum at the bottom. As soon as the screw, with the tube in which it is enclosed, begins to appear externally from the case, it folds, because it is retained by its two ligaments: nevertheless, all the internal contents continue to move gently and gradually, until the screw, piston, and bladder, are entirely come out. When that is done, the rest follow directly after. The piston separates from the barrel, and the apparent ligament, which is below the latter, swells and acquires a diameter equal to that of the spongy substance which follows it. This, although much larger than when in the case, becomes still five times longer than before. The tube which incloses it all is straightened in its middle, and forms two kinds of knots, about a third of its length distant from each extremity: the semen then flows through, and is composed of small opaque globules, which float in a serous matter, without shewing any signs of life, and which are precisely such as I have said to have seen them when they were diffused in the reservoir of the milt. In the figure, the part between the two knots seems to be broken: when it is examined attentively, we find that what causes it to appear as such, is, that the spongy substance with in the tube is broken in nearly equal pieces, which the following phenomena will clearly prove. Sometimes it happens, that the screw and the tube break by the piston, which remains in the barrel; then the tube closes in a moment, and takes a conical figure, by contracting, as much as it is possible, above the end of the screw, which demonstrates its great elasticity in that part: and the manner in which it accommodates itself with the figure of the substance it incloses, when it receives the least change, proves, that it is equal in every other respect."

Mr. Needham from this conceives that we might imagine the actions of all this machine were owing to the spring of the screw, but he proves, by many experiments, that the screw, on the contrary, only obeys a power which resides in the spongy part. As soon as the screw is separated from the rest, it ceases its action, and loses all its activity. The author afterwards makes this reflection on this singular machine:

"If, says he, I had seen the animalcule pretended to be in the semen of living animals, perhaps I might be in a condition to determine whether they are really living creatures, or simple machines prodigiously minute, and which are in miniature, what the vessels of the calmar are in the great."

By this, and some other analogies, Mr. Needham concludes, there is a great appearance that the spermatic worms of other animals are only organized bodies and machines, like to those of the calmar, whose actions are made at different times; "for, says he, let us suppose, that in the prodigious number of spermatic worms seen on the table of a microscope, there are some thousands which act at the same time, that will be sufficient to shew us, they are all alive. Let us also conceive, adds he, that the motion of these spermatic worms remains, like that of the machines of the calmar, about half a minute; then the succession of action of these small machines, will remain a long time, and the pretended animals will appear to decrease successively. Besides why should the calmar alone have machines in its seed, whereas every other animal has spermatic worms, and real animals? Analogy is here of such great weight, that it does not appear possible to refuse it." Mr. Needham likewise very justly remarks, that even the observations of Leeuwenhoek, seems to indicate that the spermatic worms have a great resemblance with the organized bodies in the seed of the calmar. "I have, says Leeuwenhoek, speaking of the cod, taken those real substances for hollow and extended animalcule, because they were four times as large as the living animalcule." And in another part, "I have remarked, he says, speaking of the seed of a dog, that the animalcules often change their form, especially when the liquor in which they float evaporates. The progressive motion does not extend above the diameter of a hair."[R]

[R] See Leeuwenh. Arch. Nat. page 306, 309, 310.

After considering all these circumstances Mr. Needham conjectures, that the supposed spermatic animals might possibly be only natural machines, substances much more simply organized than the bodies of animals. I have seen with the microscope, these machines in the calmar, and the description he gives of them, is very faithful and exact. His observations then shew us, that the seminal liquor is composed of parts which seek to be organized; that it, in fact, produces organized substances, but that they are not as yet, either animals or organized substances, like the individual which produced them. We might suppose, that these substances are only instruments which serve to perfect the seminal liquor, and strongly impel it; and that it is by their brisk and internal action, that it most intimately penetrates the seminal liquor of the female.

[CHAPTER VII.]

COMPARISON OF MY OBSERVATIONS WITH THOSE OF LEEUWENHOEK.

Although I made the preceding experiments with all the circumspection possible; and although I repeated them a number of times, I am persuaded that many things escaped my notice; I have only related what I saw, and what all the world may see, with a little art and much practice. In order to be free from prejudices, I endeavoured to forget what other naturalists asserted to have seen, conceiving that by so doing, I should be more certain of only seeing in fact what really appeared; and it was not till after I had digested my observations, that I compared them with those of Leeuwenhoek, &c. I by no means pretend to have greater abilities in microscopical observations than that great naturalist, who passed more than sixty years in making various experiments.

Notwithstanding the authority his observations may justly claim, it is surely permitted to examine and compare others with them. Truth can only be gained by such examinations, and errors discovered, particularly as we do it without any partiality, and in the sole view of establishing something fixed and certain on the nature of those moving bodies seen in the seminal liquors.

In November 1677, Leeuwenhoek, who had already communicated to the Royal Society of London many microscopical observations on the optic nerve, the blood, the juice of the plants, the texture of trees, rain-water, &c. addressed to Lord Brouncker, President of the Society, in the following words: "Postquam Exc.[S] &c. Dominus Professor Cranen me visitatione sua sæpius honorarat, litteris rogavis, Domino Ham concrato suo, quasdam observationum mearum, videndas darem. Hic dominus Ham me secundo invisens, secum in laguncula, vitrea semen viri, gonorrhæa laborantis, sponte destillatum, attulit, dicens, se post paucissimas temporis minutias (cum materia ilia jam in tantum esset resoluta ut fistulæ vitreæ immitti posset) animalcula viva in eo observasse, quæ caudam & ultra 24 horas non viventia judicabat; idem referebat se animalcula observasse mortua post sumptam ab ægroto therebintinam. Materiam prædicatam fistulæ vitreæ immissam, præsente Domino Ham, observavi, quasdamque in ea creaturas viventes, at post decursum 2 aut 3 horarum eamdem solus materiam observans, mortuas vidi.

[S] See Phil. Trans. No. 141, page 1041.

"Eamdem materiam (semen virile) non ægroti alicujus, non diuturna conservatione corruptam, vel post aliquot momenta fluidiorem factam, sed sani viri statim post ejectionem, ne interlabentibus quidem sex arteriæ pulsibus, sæpiuscule observavi, tantamque in ea viventium animalculorum multitudinem vidi, ut interdum plura quam 1000 in magnitudine arenæ sese moverent; non in toto semine, sed in materia fluida crassiori adhærente, ingentem illam animalculorum multitudinem observavi; in crassiori vero seminis materia quasi sine motu jacebant, quod inde provenire mihi imaginabar, quod materia illa crassa ex tam variis cohæreat partibus, ut animalcula in ea se movere nequirent; minora globulis sanguini ruborem adferentibus hæc animalcula erant, ut judicem, millena millia arenam grandiorem magnitudine non æquatura. Corpora corum rotunda, anteriora obtusa, posteriora ferme in aculeum desinentia habebant; cauda tenui longitudine corpus quinquies sexiesve excedente, & pellucida crassitiem vero ad 25 partem corporis habente prædita erant, adeo ut ea quoad figuram cum cyclaminis minoribus, longam caudam habentibus, optime, comparare queam; motu caudæ serpentino, aut ut anguillæ in aqua natantis progrediebantur; in materia vero aliquantulum crassiori caudam octies deciesve quidem evibrabant antequam latitudinem capilli procedebant. Interdum mihi imaginabar me internoscere posse adhuc varias in corpore horum animalculorum partes, quia vero continuo eas videre nequibam, de iis tacebo. His animalculis minora adhuc animalcula, quibus non nisi globuli figuram attribuere possum, permissa erant.

"Memini me ante tres aut quatuor annos, rogatu Domini Oldenburg, B. M. semen virile observasse, & prædicta animalia pro globulis habuisse; sed quia fastidiebam ab ulteriori inquisitione, & magis quidem a descriptione, tunc temporis eam omisi. Jam quoad partes ipsas, ex quibus crassam seminis materiam, quoad majorem sui partem consistere sæpius cum admiratione observavi, ea sunt tam varia ac multa vasa, imo in tanta multitudine hæc vasa vidi, ut credam me in unica seminis gutta plura observasse quam anatomico per integrum diem subjectum aliquod secanti occurrant. Quibus visis, firmiter credebam nulla in corpore humano jam formato esse vasa, quæ in semine virili bene constituto non reperiantur. Cum materia hæc per momenta quædam aëri fuisset exposita, prædicta vasorum multitudo in aquosam magnis oleaginosis globulis permistam materiam mutabatur, &c."

The Secretary of the Royal Society, in answer to this letter, says, that it would be proper to make the like experiments on the seed of other animals, as dogs, horses, &c. not only to form a better judgment on the first discovery, but to know the differences which might be found in the number, and the figure of those animalcules. And with relation to the vessels of the thickest part of the seminal liquors, he greatly doubts they were only filaments without any organization, "quæ tibi videbatur vasorum congeries, fortassis seminis sunt quædam filamenta, haud organice constructa, sed dum permearunt vasa generationi inservientia in istiusmodi figuram elongata. Non dissimili modo ac sæpius notatus sum salivam crassiorem ex glandularum faucium foraminibus editam quasi e convolutis fibrilis constantem."[T]

[T] See the Secretary's answer to Leeuwenhoek's Letter in the Phil. Trans. No. 141, page 1043.

Leeuwenhoek answered him on the 18th of March, 1678, in the following words: "Si quando canes coeunt marem a fœmina statim seponas materia quædam tenuis & aquosa (lympha scilicet spermatica) e pene solet paulatim exstillare; hanc materiam numerosissimis animalculis repletam aliquoties vidi, eorum magnitudine quæ in semine virili conspiciuntur, quibus particulæ globulares aliquot quinquagies majores permiscebantur.

"Quod ad vasorem in crassiori seminis virilis portione spectabilium observationem attinet, denuo non semel iteratam, saltem mihimetipsi comprobasse videor; meque omnino persuasum habeo, cuniculi, canis, felis, arterias venasve fuisse a peritissimo anatomico haud unquam magis perspicue observatas, quam mihi rasa in semine virili, ope perspicilli, in confectum venere.

"Cum mihi prædicta vasa primum innotuere, statim etiam pituitam, tum & salivam perspicillo applicavi; verum his minime existentia animalia frustra quæsivi.

"A cuniculorum coitu lymphæ spermaticæ guttulam, unam et alteram, e femella exstillantem, examini subjeci, ubi animalia prædictorum similia, sed longe pauciora, comparuere. Globuli item quam plurimi, plerique magnitudine animalium, iisdem permisti sunt.

"Horum animalium aliquot etiam delineationes transmisi, figura a ([plate 3.]) exprimit corum aliquot vivum (in semine cuniculi arbitror) eaque forma qua videbatur, dum aspicientem me versus tendit. A B C, capitulum cum trunco indicant; C D, ejusdem caudam, quam pariter ut suam anguilla inter natandum vibrat. Horum millena millia, quantum conjectare est, arenulæ majoris molem vix superant, ([fig. b, c, d,]) sunt ejusdem generis animalia, sed jam mortua.

PLATE. III.

"([Fig. e.]) Delineatur vivum animalculum, quemadmodum in semine canino sese aliquoties mihi attentius intuenti exhibuit. E F G, caput cum trunco indigitant, G H ejusdem caudam, ([fig. f, g, h,]) alia sunt in semine canino quæ motu & vita privantur, qualium etiam vivorum numerum adeo ingentem vidi, ut judicarem portionem lymphæ spermaticæ arenulæ mediocri respondentem, eorum ut minimum decena millia continere."

By another letter written to the Royal Society, the 31st of May, 1678, Leeuwenhoek adds, "Seminis canini tantillum microscopio applicatum iterum contemplatus sum, in eoque antea descripta animalia numerosissime conspexi. Aqua pluvialis pari quantitate adjecta, iisdem confestim mortem accersit. Ejusdem seminis canini portiuncula in vitreo tubulo unciæ partem duodecimalem crasso servata, sex & triginta horarum spatio contenta animalia vita destitua pleraque, reliqua moribunda videbantur.

"Quo de vasorum in semine genitali existentia magis constaret, delineationem eorum aliqualem mitto, ut in figura ABCDE, ([fig. i.]) quibus literis circumscriptum spatium arenulam mediocrem vix superat."

I have copied these first remarks of Leeuwenhoek from the Philosophical Transactions, because, in matters of this kind, observations made without any systematical view are those which are the most faithfully described, and even this able naturalist no sooner formed a system on spermatic animals, than he began to vary in essential points.

It is evident by the above dales, that Hartsoeker is not the first who published, if he was the first who discovered spermatic animals. In the Journal de Sçavans, in the year 1774, there is a letter from Mr. Huguens, on the subject of a microscope, made by one small ball of glass, with which he asserts he perceived animals in the water, wherein pepper had been infused for two or three days, as Leeuwenhoek before had observed with the like microscopes, but whose balls were not so minute. "There are also other seeds, he continues, which engender such animals, as coriander seeds, &c. and I have seen the same thing in the pith of the birch tree, after having kept it for four or five days; and some have observed them in the water where nutmegs and cinnamon have been soaked. These animals may be said to engender from some corruption or fermentation: but there are others which must have a different origin; as those in the seed of animals, which seem in such great numbers, as to be almost composed of them; they are all transparent, have a quick motion, and their figures are like the tadpole."

Huguens does not mention the author of this discovery; but in the Journal of the 29th of August in the same year, there is an extract of a letter of M. Hartsoeker, in which he gives the method of forming these glass balls by means of the flame of a lamp; and the author of the Journal says, "By this method he has discovered that little animals are engendered in urine which has been kept for some days, and have the figure of little eels: he found some in the seed of a cock, which appeared of the same form, but quite different from those found in the seed of other animals, which resemble tadpoles, or young frogs, before their legs are formed." The author seems to attribute the invention to Hartsoeker; but if we reflect on the uncertain manner in which it is there represented, and on the particular manner in which Leeuwenhoek speaks in his letter, written and published above a year before, we must allow him to be the first who made this observation; but between them a contest took place as to the discovery which has never been decided. Be this as it will, Leeuwenhoek was undoubtedly the first inventor of the microscope, whose focuses are balls of glass formed by the flame of a lamp. But to return to his observations.

I shall first remark, that what he says of the number and motion of these pretended animals is true; but the figure of the body is not always the same as he describes it: sometimes the part which precedes the tail is round and at others long; often flat, and frequently broader than it is long, &c. and with respect to the tail, it is often much larger and shorter than he asserts. The motion of vibrations which he gives to the tail, and by means of which he pretends that the animalcules advance progressively in this fluid, has never appeared to me as he has described it. I have seen these moving substances make eight or ten oscillations from the right to the left, or vice versa, without advancing the breadth of a hair; and I have even seen many more which could not advance at all; because this tail, instead of being of any assistance to them was, on the contrary, a thread attached either in the filaments or mucilaginous parts of the liquor, and rather retained the moving substance like as a thread fastened to the point retains the ball of a pendulum; and when this tail had any motion, it only resembled a thread which forms a curve at the end of an oscillation. I have seen these threads, or tails, fastened to the filaments which Leeuwenhoek stiles vessels; I have seen them separate after many reiterated efforts of the moving bodies; I have seen them at first lengthen, then diminish, and at last totally disappear. I therefore think these tails should be considered as accidental parts, and not as essential to the bodies of these pretended animals. But what is most remarkable, Leeuwenhoek precisely says, in his letter to Lord Brouncker, that, besides these animals that had tails, there were also smaller animals in this liquor, which had no other form than that of a globule. "His animalculis (caudatis scilicet) minora adhuc animalcula, quibus non nisi globuli figuram attribuere possum, permista erant." This is the truth; but after Leeuwenhoek had advanced that these animals were the only efficient principle of generation, and that they were transformed into human figures, he has only regarded those as animals which had tails; and as it was consistent for animals that were transformed into human figures, to have a constant form, he never afterwards mentions those smaller animalcules without tails; and I was greatly surprised, on comparing the copy of this letter with that he published twenty years after, in his 3d volume, where, instead of the above words, the following are found: "Animalculis hisce permistæ jacebant aliæ minutiores particulæ, quibus non aliam quam globulorum seu sphæricam figuram assignare queo;" which is quite different. A particle of matter to which he attributes no motion, is very different from an animalcule: and it is astonishing that Leeuwenhoek, in copying his own works, has altered this essential article. What he adds immediately after likewise merits attention: he says, that by the desire of Mr. Oldenburg he had examined this liquor three or four years before, when he took these animalcules for globules; that is, there are times when these pretended animalcules are no more than globules, without any remarkable motion, and others when they move with great activity; sometimes they have tails, and at others they have none. Speaking in general of spermatic animals he says, "Ex hisce meis observationibus cogitare cœpi, quamvis antehac de animalculis in seminibus masculinis agens, scripserim, me in illis caudas non detexisse, fieri tamen posse ut illa animalcula æque caudis fuerint instructa ac nunc comperi de animalculis in gallorum gallinaceorum semine masculino;" another proof that he has often seen spermatic animals of all kinds without tails.

In the second place we must remark, that the filaments which are seen in the seminal liquor before it is liquefied were discovered by Leeuwenhoek, and that in his first observations, before he had made any hypothesis on spermatic animals, he considered these filaments as veins, nerves, and arteries; and firmly believed all the parts and vessels of the human body might clearly be seen in the seminal liquor. This opinion he persisted in, in defiance of the representations which Oldenburg made to him on this subject from the Royal Society: but as soon as he thought of transforming these pretended spermatic animals into men, he no longer mentioned these vessels; and instead of looking on them as nerves, arteries, and veins, of the human body already formed in the seed; he did not even attribute to them the functions they really possess, the producing of these moving bodies: and he says, vol. I. p. 7, "Quid fiet de omnibus illis particulis seu corpusculis præter illa animalcula semini virili hominum inhærentibus? Olim & priusquam hæc scriberem, in ea sententia fui, prædictas strias vel vasa ex testiculis principium secum ducere, &c." And in another part he says, that if he had formerly written any thing on the subject of these vessels found in the seed, we must pay no attention to it.

We shall observe in the third place, that if we compare the figures a, b, c, d, ([PLATE III.]) copied from the Philosophical Transactions, with those which Leeuwenhoek had engraved many years after, ([PLATE IV.]) we shall find considerable difference, especially in the figures of the dead animals, of a rabbit and in those of a dog, (which plate we have also copied for the satisfaction of our readers) from all which we may conclude, that Leeuwenhoek has not always observed objects entirely alive: that the moving bodies, which he looked upon as animals, appeared to him under different forms; and that he has varied in his assertions, with a view of making the species of men and animals perfectly consistent; he has not only varied in the basis of these experiments, but even in the manner of making them, for he expressly says, that he always diluted the liquor with water, in order to separate, and to give more motion to these animalcules: nevertheless, in his letter to Lord Brouncker, he says, that having mingled an equal quantity of rain water with the seminal liquor of a dog, in which he had before perceived an infinity of living animalcules, yet the mixing of this water killed them. The first experiment of Leeuwenhoek's therefore was made, like mine, without any mixture; and it even seems, that he was not of opinion to mix any water with the liquor till a long time after; because he thought he had discovered, by his first essay, that water caused the death of the animalculæ; which however is not the fact. I think that the mixture of the water only dissolves the filaments very suddenly; for I have seen but very few filaments in all the experiments I have made after mixing the water with the seminal liquor.

As soon as Leeuwenhoek was persuaded that spermatic animals were transformed into men, and other animals, he imagined he saw two sorts in the seminal liquor of every animal, the one male, and the other female; and this difference, according to him, served not only for the generation of themselves, but for the production of males and females, which was very difficult to conceive by a simple transformation. He speaks of the male and female animalcule, in his letter printed in the Philosophical Transactions, No. 145, and in many parts of his works,[U] but he does not describe the difference of these male and female animalcules, and which in fact never existed but in his own imagination.

[U] See vol I. page 163, and vol. III. page 101, of his works.

The famous Boerhaave having asked Leeuwenhoek, if he had not observed in spermatic animals different degrees of growth and size? Leeuwenhoek answered, that having dissected a rabbit, he observed in the semen an infinite number of living animals. "Incredibilem, says he, viventium animalculorum, numerum conspexerunt, cum hæc animalcula scypho imposita vitreo & illic emortua, in rariores ordines disparassent, & per continuos aliquot dies sæpius visu examinassem, quædam ad justam magnitudinem nondum excrevisse adverti. Ad hæc quasdam observavi particulas perexiles & oblongas, alias aliis majores, &, quantum oculis apparebat, cauda destitutas; quas quidem particulas non nisi animalcula esse credidi, quæ ad justam magnitudinem non excrevissent."[V] Here then are animalcules of different sizes, some with tails and others without, which much better agrees with my experiments, than with Leeuwenhoek's own system. We differ only in one particular; he says, that those without tails were young animalculæ, which were not arrived at their full growth; while I, on the contrary, have seen these pretended animals quit the filaments with tails or threads, and afterwards lose them by degrees.

[V] See vol. IV. pages 280 and 281.

In the same letter to Boerhaave, he says, in the semen of a ram, he perceived animalcules following each other in swarms like a flock of sheep. "A tribus circiter annis testes arietis, adhuc calentes, ad ædes meas deferri curaveram, cum igitur materiam ex epididymibus eductam, ope microscopii contemplarer, non sine ingenti voluptate advertebam animalcula omnia, quotquot innatabant semini masculino, eundem natando cursum tenere, ita nimirum ut quo itinere priora prinatarent eodem posteriora subsequerentur, adeo ut hisce animalculis quasis sit ingenitum, quod oves factitare vidimus, scilicet ut precedentium vestigiis grex universus incedat." This observation, which Leeuwenhoek made in 1713, and which he looks upon as singular and novel, proves to me, that he had never examined the seminal liquors of animals with attention, at least sufficient to give very exact descriptions of them. Leeuwenhoek was sixty-one years old in 1713, had made microscopical observations for more than forty-five years, had published the discovery of spermatic animals for about thirty-six years, and then, for the first time, saw in the seminal liquor of a ram, what is seen in all seminal liquors, and what I have described in Experiment [IX] in the seed of a man; Experiment [XII] in the seed of a dog; and in Experiment [XXIX] in that of a bitch. It is not necessary to suppose the spermatic animals of the ram are endowed with instinct, to explain the floating of these animals, in flocks like sheep, since those of a man, dog, or bitch, does the same; and which motion depends solely on particular circumstances, whose principle is, that all the fluid matter of the seed is on one side, while the thick matter is on the other; for then all the bodies in motion will be disengaged from the mucilage, and follow the same road into the most fluid part of the liquor.

In another letter, written the same year, to Boerhaave, he relates some further observations he made on rams, and says, that he has seen, in the vasa deferentia, flocks of animals which float all on one side, and others which go in a contrary direction; and he adds, "Neque illud in unica epididymum parte, sed & in aliis quas præcideram partibus, observavi. Ad hæc, in quadam parastatarum resecta portione complura vidi animalcula, quæ necdum in justam magnitudinem adoleverant, nam et corpuscula illis exiliora & caudæ triplo breviores erant quam adultis. Ad hæc, caudas non habebant desinentes in mucronem, quales tamen adultis esse passim comperio. Præterea in quandam parastatarum portionem incidi, animalculis quantum discernere potui, destitutam, tantum illi quædam perexiguæ inerant particulæ, partim longiores, partim breviores, sed altera sui extremitate crassiunculæ; istas particulas in animalcula transituras esse non dubitabam." It is easy to see, by this passage, that Leeuwenhoek had seen, in this seminal liquor, what I found in all; that is to say, moving bodies of different sizes, figures, and motions; and which agrees much better with the idea of organic particles in motion than of that with real animals.

It appears, therefore, that Leeuwenhoek's observations are not contrary to mine, although he has drawn very different conclusions from them. I am persuaded that if any person would take the trouble of making the like experiments they would not have any difficulty in discovering from whence these differences proceed, and would find that I have advanced nothing which is not conformable to truth; and to enable the reader to decide thereon, I shall subjoin a few remarks.

The filaments I have spoken of are not always to be perceived in the seminal liquor of a man. To discover them it must be examined the moment it is taken from the body, and even then it will sometimes happen that there is not one to be seen. Sometimes the seminal liquor presents, especially when it is very thick, only large globules, which may be even distinguished with a common lens. By inspecting them with the microscope they appear like young oranges; they are very opaque, and a single one often fills up the whole table of the microscope. The first time I saw these globules I thought they were some foreign matters fallen into the liquor, but having examined different drops I discovered that the whole was composed of these thick globules. I selected one of the roundest, and whose size was such that, its centre being in the middle of the table of the microscope, I could at the same time observe the whole circumference; at first it was absolutely opaque; a short time afterwards I perceived a bright luminous ring to form on its surface, which remained about half an hour, and then approached by degrees towards the centre, which became clear, and of different colours, while the remainder of the globule continued opaque. This light, which brightened in the centre of the globule, resembled those seen in the great air bubbles. The globule then began to get a little flat, and acquire a small degree of transparency. Having examined it more than three hours I perceived no more alteration, nor any appearance of motion, either internally or externally. I then imagined, that by mixing this liquor with water, these globules might be changed; in fact they did change, but they presented only a transparent and homogeneous liquor, wherein was nothing remarkable. I suffered the seminal liquor to liquefy of itself, and examined it at the end of six, twelve, and twenty-four hours, but saw nothing more than a fluid; without the smallest resemblance of life or motion. I only relate this observation to shew that there are times when the common phenomena are not to be seen in the seminal liquor.

At times all the moving bodies appear to have tails, especially in the semen of a man and a dog; the motion is then the least brisk, and performed with difficulty. If this liquor is suffered to dry, the tails or threads are deprived of motion the first; the anterior extremity continues to vibrate for some time, and then all motion entirely ceases. These substances may be preserved in this state of dryness for a long time: if a small drop of water is mixed therewith, their figure changes, they are reduced into many globules, which sometimes appear to be in motion, as well by their approximation to each other, as by the trepidation and twirling round their centres.

These moving bodies in the seminal liquor of a man, dog, or bitch, so nearly resemble each other, as to admit of mistaking one for the other, especially if they are examined the moment the liquor is drawn from the animal. Those of the rabbit appear smaller and brisker; but these differences proceed more from the different states in which the liquor is at the time of observation, than from the nature of the liquor itself, which ought to be different in different kinds of animals; for example, in that of a man I have seen streaks of thick filaments, ([fig. 3.]) and have perceived the moving bodies separate themselves from these filaments from whence they appeared to proceed; but I have never seen any thing like it in the semen of a dog; where, instead of filaments, or separated streaks, it is commonly a mucilage whose texture is more compact, and in which we with difficulty discern any filamentary parts; yet this mucilage gives birth to moving bodies like those in the semen of men.

The motions of these bodies remain a longer time in the liquor of a dog, than in that of a man; from which it is more easy to be certain of the alteration of form above mentioned. The moment the liquor issues from the body of the animal we perceive the animalcules to have tails; in twelve, twenty-four, or thirty-six hours after, we shall find they have lost those tails, and are then no more than ovals in motion, often much brisker than at first.

The moving bodies are always a little below the surface of the liquor. On the surface some large transparent air bubbles, which have no motion, generally appear, though sometimes these bubbles stir and seem to have a progressive motion, but which is nothing more than the agitation of the air. Below the moving substances we often see others much smaller, and which only appear like globules, having no tails, but the greatest number of which are oftentimes in motion. I have also generally remarked, that in the infinite number of globules, in all those liquors, those which are very small, are commonly black, or darker than the rest; and that those which are extremely minute and transparent, have but little or no motion; they appear also to weigh specifically heavier, for they are always the deepest in the liquor.

[CHAPTER XIII.]

REFLECTIONS ON THE PRECEDING EXPERIMENTS.

By the experiments we have just described, I was assured that females, as well as males, have a seminal liquor which contains moving substances; that these substances were not real animals, but only living organic particles; and that those particles exist, not only in the seminal liquors of the two sexes, but even in the flesh of animals, and in the germs of vegetables. To discover whether all the parts of animals, and all the germs of vegetables, contained living organic particles, I caused infusions of the flesh of different animals to be made, and of more than twenty kinds of seeds of different plants; and after they had infused four or five days, in phials closely stopt up, I had the satisfaction to see moving organic parts in them all; some appeared sooner, and others later; some preserved their motion for months together, while others were soon deprived of it; some directly produced large moving globules, that had the appearance of real animals, which changed their figures, separated, and became successively smaller: others produced only small globules, whose motions were very brisk; others produced filaments which lengthened and seemed to vegetate, swelled, and afterwards thousands of moving globules issued therefrom; but it is useless to detail my observations on the infusion of plants, since Mr. Needham has published so excellent a treatise on the subject. I read the preceding treatise to that able naturalist, and often reasoned with him on the subject, particularly on the probability that the germs of vegetables contained similar moving bodies to those in the seed of male and female animals. He thought those views sufficiently founded to deserve to be pursued; and therefore began to make experiments on all parts of vegetables; and I must own that the ideas I gave him on this subject have reaped greater profit under his hands than they would have done from me. I could quote many examples, but shall confine myself to one, because I indicated the circumstance I am going to relate.

To determine whether the moving substances seen in the infusions of flesh were true animals, or only, as I supposed, moving organic particles, Mr. Needham imagined that he had only to examine some roasted meat, because if they were animals the fire must destroy them; and if not animals, they might still be found there as well as when the meat was raw; having therefore taken the jelly of veal, and other roasted meat, he infused them for several days in water, closely corked up in phials, and upon examination he found in every one of them a great quantity of moving substances. He shewed me some of these infusions, and among the rest that of the jelly of veal, in which there were moving substances, perfectly like those in the seminal liquor of a man, a dog, and a bitch, when they have no threads, or tails; and although we perceived them to change their figures, their motions so perfectly resembled those of an animal which swims, that whoever saw them, without being acquainted with what has been already mentioned, might certainly have taken them for real animals. I shall only add, that Mr. Needham assured himself, by a multiplicity of experiments, that all parts of vegetables contain moving organic particles, which confirms what I have said, and extends my theory on the composition of organized beings, and their reproduction.

All animals, both male and female, and all vegetables whatsoever, it is therefore evident are composed of living organic parts. These organic parts are in the greatest abundance in the seminal liquor of animals, and in seeds of vegetables. It is from the union of these organic parts returned from all parts of the animal or vegetable body, that reproduction is performed, and is always like the animal or vegetable in which it operates; because the union of these organic parts cannot be made but by the means of an internal mould, in which the form of an animal or vegetable is produced. It is in this also the essence of the unity and continuity of the species consists, and will so continue while the great Creator permits their existence.

But before I draw general conclusions from the system I am establishing, I must endeavour to remove some objections which might be made, and mention some other circumstances which will serve to place this matter in a better light.

It will be asked, why I deny those moving substances in the seminal liquors to be animals, since they have constantly been regarded as such by Leeuwenhoek, and every other naturalist, who has examined them? I may also be told, that living organic particles are not perfectly intelligible, if they are to be looked upon as animalculæ; and to suppose an animal is composed of a number of small animals, is nearly the same as saying that an organized being is composed of living organic particles. I shall therefore endeavour to answer these objections in a satisfactory manner.

It is certain that almost all naturalists agree in looking on the moving substances in seminal liquors as real animals; but it is no less certain, from my own observations, and those of Mr. Needham, on the seed of the calmar, that these moving substances are more simple and less organized beings than animals.

The word animal, in the acceptation we commonly receive it, represents a general idea formed of particular ideas drawn from particular animals. All general ideas include many different ones, which approach, or are more or less distant from each other, and consequently no general idea can either be exact or precise. The general idea which we form of an animal may be taken principally from the particular idea of a dog, a horse, and other beasts, which appear to us to act and move according to the impulse of their will, and which are besides composed of flesh and blood, seek after their food, have sexes, and the faculty of reproduction. The general idea, therefore, expressed by the word animal, must comprehend a number of particular ideas, not one of which constitutes the essence of the general idea, for there are animals which appear to have no reason, will, progressive motion, flesh nor blood, and which only appear to be a congealed substance: there are some which cannot seek their food, but only receive it from the element they live in: there are some which have no sensation, not even that of feeling, at least in any sensible degree: there are some have no sexes, or are both in one; there only belongs, therefore, to the animal a general idea of what is common also to the vegetable, that is, the faculty of reproduction.

The general idea then is formed from the whole taken together, which whole being composed of different parts, there is consequently between these parts degrees and links. An insect, in this sense, is something less of an animal than a dog; an oyster still less than an insect; a sea-nettle, or a fresh-water polypus, still less than an oyster; and as nature acts by insensible links, we may find beings which are still less animated than a sea-nettle, or a polypus. Our general ideas are only artificial methods to collect a quantity of objects in the same point of view; and they have, like the artificial methods we shall speak of, the defect of never being able to comprehend the whole. They are likewise opposite to the walk of nature, which is uniform, insensible, and always particular, insomuch that by our endeavouring to comprehend too great a number of particular ideas in one single word, we have no longer a clear idea of what that word conveys; because, the word being received, we imagine that it is a line drawn between the productions of nature; that all above this line is animal, and all below it vegetable; another word, as general as the first, and which is used as a line of separation between organized bodies and inanimate matter. But as we have already said, these lines of separation do not exist in nature; there are beings which are neither animals, vegetables, nor minerals, and which we in vain might attempt to arrange with either. For example, when Mr. Trembly first observed the polypus, he employed a considerable time before he could determine whether it was an animal or a plant; and possibly from this reason that it is perhaps neither one nor the other, and all that can be said is, that it approaches nearest to an animal; and as we suppose every living thing must be either an animal or a plant, we do not credit the existence of an organized being, that cannot be referred to one of those general names; whereas there must, and in fact are, a great number of organized beings which are neither the one nor the other. The moving substances perceived in seminal liquors, in infusions of the flesh of animals, in seed, and other parts of plants, are all of this kind. We cannot call these animals, nor can we say they are vegetables, and certainly we can still less assert they are minerals.

We can therefore affirm, without fear of advancing too much, that the grand division of nature's productions into Animals, Vegetables, and Minerals, do not contain every material being; since there are some that exist which cannot be classed in this division. We have already observed, that nature passes by insensible links from the animal to the vegetable, but from the vegetable to the mineral the passage is quick, and the distance considerable; from whence the law of nature's passing by imperceptible degrees appears untrue. This made me suppose that by examining nature closely we shall discover intermediate organized beings, which without having the power of reproduction, like animals and vegetables, would nevertheless have a kind of life and motion; other beings which, without being either vegetables or animals, might possibly enter into the composition of both, and likewise other beings which would be only the assemblage of the organic molecules I have spoken of in the preceding chapters.