SLEEP AND ITS DERANGEMENTS.

SLEEP
AND
ITS DERANGEMENTS.

BY
WILLIAM A. HAMMOND, M.D.,
PROFESSOR OF DISEASES OF THE MIND AND NERVOUS SYSTEM, AND OF CLINICAL MEDICINE
IN THE BELLEVUE HOSPITAL MEDICAL COLLEGE, NEW YORK; VICE-PRESIDENT OF
THE ACADEMY OF THE MEDICAL SCIENCES, NATIONAL INSTITUTE
OF LETTERS, ARTS, AND SCIENCES; LATE SURGEON-GENERAL
U. S. ARMY, ETC. ETC.

PHILADELPHIA:
J. B. LIPPINCOTT & CO.
1869.

Entered, according to Act of Congress, in the year 1869, by
J. B. LIPPINCOTT & CO.,
In the Clerk’s Office of the District Court of the United States for the
Eastern District of Pennsylvania.

PREFACE.

The basis of this little volume is a paper on Insomnia, published in the New York Medical Journal in May and June, 1865. This was subsequently enlarged and published in a separate form, under the title “Wakefulness, with an Introductory Chapter on the Physiology of Sleep.”

The very favorable reception which it met with in this country, in Great Britain, and on the Continent, from the medical press, the profession, and the public generally, led to the exhaustion of a large edition in a few months.

The present issue was announced nearly two years ago, and the printing begun. Increasing professional duties have, however, prevented me bestowing that continuous labor upon it which was desirable, and hence the publication has been long delayed. My apologies therefore are due, first, to my excellent and dear friend, the senior member of the house of J. B. Lippincott & Co., whose patience I know has been severely tried, but who has scarcely reproached me for my neglect; and second, to that portion of the public which has been kind enough to make repeated inquiries relative to the appearance of this monograph, and which I trust will not be disappointed, now that it is really published.

162 West 34th St., New York,
July 10th, 1869.

CONTENTS.

SLEEP AND ITS DERANGEMENTS.

CHAPTER I.

THE NECESSITY FOR SLEEP.

The state of general repose which accompanies sleep is of especial value to the organism in allowing the nutrition of the nervous tissue to go on at a greater rate than its destructive metamorphosis. The same effect is, of course, produced upon the other structures of the body; but this is not of so much importance as regards them, for while we are awake they all obtain a not inconsiderable amount of rest. Even those actions which are most continuous, such as respiration and the pulsation of the heart, have distinct periods of suspension. Thus, after the contraction and dilatation of the auricles and ventricles of the heart, there is an interval during which the organ is at rest. This amounts to one-fourth of the time requisite to make one pulsation and begin another. During six hours of the twenty-four the heart is, therefore, in a state of complete repose. If we divide the respiratory act into three equal parts, one will be occupied in inspiration, one in expiration, and the other by a period of quiescence. During eight hours of the day, therefore, the muscles of respiration and the lungs are inactive. And so with the several glands. Each has its time for rest. And of the voluntary muscles, none, even during our most untiring waking moments, are kept in continued action.

But for the brain there is no rest, except during sleep, and even this condition is, as we all know, only one of comparative quietude in many instances. So long as an individual is awake, there is not a single second of his life during which the brain is altogether inactive; and even while he is deprived by sleep of the power of volition, nearly every other faculty of the mind is capable of being exercised; and several of them, as the imagination and memory, for instance, are sometimes carried to a pitch of exaltation not ordinarily reached by direct and voluntary efforts. If it were not for the fact that all parts of the brain are not in action at the same time, and that thus some slight measure of repose is afforded, it would probably be impossible for the organ to maintain itself in a state of integrity.

During wakefulness therefore the brain is constantly in action, though this action may be of such a character as not always to make us conscious of its performance. A great deal of the power of the brain is expended in the continuance of functional operations necessary to our well-being. During sleep these are altogether arrested or else very materially retarded in force and frequency.

Many instances of what Dr. Carpenter very happily calls “unconscious cerebration” will suggest themselves to the reader. We frequently find suggestions occurring to us suddenly—suggestions which could only have arisen as the result of a train of ideas passing through our minds, but of which we have been unconscious. This function of the brain continues in sleep, but not with so much force as during wakefulness. The movements of the heart, of the inspiratory muscles, and of other organs which perform either dynamic or secretory functions are all rendered less active by sleep; and during this condition the nervous system generally obtains the repose which its ceaseless activity during our periods of wakefulness so imperatively demands. Sleep is thus necessary in order that the body, and especially the brain and nervous system, may be renovated by the formation of new tissue to take the place of that which by use has lost its normal characteristics.

From what has been said it will be seen that the brain is no exception to the law which prevails throughout the whole domain of organic nature—that use causes decay. The following extract from another work[1] bears upon this point, and I think tends to its elucidation.

“During life the fluids and tissues of the body are constantly undergoing change. New matter is deposited, and the old is removed with ceaseless activity. The body may be regarded as a complex machine, in which the law, that force is only generated by decomposition, is fully carried out. Every motion of the body, every pulsation of the heart, every thought which emanates from the encephalon is accompanied by the destruction of a certain amount of tissue. As long as food is supplied in abundance, and the assimilative functions are not disordered, reparation proceeds as rapidly as decay, and life is the result; but should nutrition be arrested, by any cause, for any considerable period, new matter ceases to be formed, and the organs, worn out, act no longer, and death ensues.

“The animal body differs from any inorganic machine in the fact that it possesses the power of self-repair. In the steam-engine, for instance, the fuel which serves for the production of steam, and subsequently for the creation of force, can do nothing toward the repair of the parts which have been worn out by use. Day by day, by constant attrition and other causes, the engine becomes less perfect, and eventually must be put in order by the workman. In the animal body, however, the material which serves for the production of force is the body itself, and the substances which are taken as food are assimilated according to their character by those organs and parts which require them.

“The body is therefore undergoing continued change. The hair of yesterday is not the hair of today; the muscle which extends the arm is not identically the same muscle after as before its action; old material has been removed and new has been deposited to an equal extent; and though the weight and form, the chemical constitution and histological character have been preserved, the identity has been lost.”

All this is especially true of the brain. Its substance is consumed by every thought, by every action of the will, by every sound that is heard, by every object that is seen, by every substance that is touched, by every odor that is smelled, by every painful or pleasurable sensation, and so each instant of our lives witnesses the decay of some portion of its mass and the formation of new material to take its place. The necessity for sleep is due to the fact that during our waking moments the formation of the new substance does not go on as rapidly as the decay of the old. The state of comparative repose which attends upon this condition allows the balance to be restored, and hence the feeling of freshness and rejuvenation we experience after a sound and healthy sleep. The more active the mind the greater the necessity for sleep, just as with a steamer, the greater the number of revolutions its engine makes, the more imperative is the demand for fuel.

The power with which this necessity can act is oftentimes very great, and not even the strongest exertion of the will is able to neutralize it. I have frequently seen soldiers sleep on horseback during night marches, and have often slept thus myself. Galen on one occasion walked over two hundred yards while in a sound sleep. He would probably have gone farther but for the fact of his striking his foot against a stone and thus awaking.

The Abbé Richard states that once when coming from the country alone and on foot, sleep overtook him when he was more than half a league from town. He continued to walk, however, though soundly asleep, over an uneven and crooked road.[2]

Even when the most stirring events are transpiring, some of the participants may fall asleep. Sentinels on posts of great danger cannot always resist the influence. To punish a man with death, therefore, for yielding to an inexorable law of his being, is not the least of the barbarous customs which are still in force in civilized armies. During the battle of the Nile many of the boys engaged in handing ammunition fell asleep, notwithstanding the noise and confusion of the action and the fear of punishment. And it is said that on the retreat to Corunna whole battalions of infantry slept while in rapid march. Even the most acute bodily sufferings are not always sufficient to prevent sleep. I have seen individuals who had been exposed to great fatigue, and who had while enduring it met with accidents requiring surgical interference, sleep through the pain caused by the knife. Damiens, who attempted the assassination of Louis XV. of France, and who was sentenced to be torn to pieces by four horses, was for an hour and a half before his execution subjected to the most infamous tortures, with red-hot pincers, melted lead, burning sulphur, boiling oil, and other diabolical contrivances, yet he slept on the rack, and it was only by continually changing the mode of torture, so as to give a new sensation, that he was kept awake. He complained, just before his death, that the deprivation of sleep was the greatest of all his torments.

Dr. Forbes Winslow[3] quotes from the Louisville Semi-Monthly Medical News the following case:

“A Chinese merchant had been convicted of murdering his wife, and was sentenced to die by being deprived of sleep. This painful mode of death was carried into effect under the following circumstances: The condemned was placed in prison under the care of three of the police guard, who relieved each other every alternate hour, and who prevented the prisoner falling asleep night or day. He thus lived nineteen days without enjoying any sleep. At the commencement of the eighth day his sufferings were so intense that he implored the authorities to grant him the blessed opportunity of being strangled, guillotined, burned to death, drowned, garroted, shot, quartered, blown up with gunpowder, or put to death in any conceivable way their humanity or ferocity could invent. This will give a slight idea of the horrors of death from want of sleep.”

In infants the necessity for sleep is much greater than in adults, and still more so than in old persons. In the former the formative processes are much more active than those concerned in disintegration. Hence the greater necessity for frequent periods of repose. In old persons, on the contrary, decay predominates over construction, there is a decreased activity of the brain, the nervous system, and of all other organs, and thus the demand for rest and recuperation is lessened.

The necessity for sleep is not felt by all organic beings alike. The differences observed are more due to variations in habits, modes of life, and inherent organic dispositions, than to any inequality in the size of the brain, although the latter has been thought by some authors to be the cause. It has been assumed that the larger the brain the more sleep was required. Perhaps this is true as regards the individuals of any one species of animals, but it is not the case when species are compared with each other. In man, for instance, persons with large heads, as a rule, have large, well-developed brains, and consequently more cerebral action than individuals with small brains. There is accordingly a greater waste of cerebral substance and an increased necessity for repair.

This is not, however, always the case, as some individuals with small brains have been remarkable for great mental activity.

All animals sleep, and even plants have their periods of comparative repose. As Lelut says:[4]

“No one is ignorant of the nocturnal repose of plants. I say repose and nothing else. I do not say diminution or suspension of their sensibility, for plants have no sensibility. I say diminution of their organic actions—a diminution which is evident and characteristic in all, more evident and more characteristic in some. * * *

“Their interior or vital movements are lessened, the flow of the sap and of other fluids which penetrate and rise in them is retarded. Their more mobile parts—the leaves, the flowers—show by their falling, their occlusion, their inclination that their organic actions are diminished, and that a kind of repose has been initiated, which takes the place of the lying down, which, with animals, is the condition and the result of sleep.”

CHAPTER II.

THE CAUSES OF SLEEP.

The exciting cause of natural and periodic sleep is undoubtedly to be found in the fact that the brain at stated times requires repose, in order that the cerebral substance which has been decomposed by mental and nervous action may be replaced by new material. There are other exciting causes than this, however, for sleep is not always induced by ordinary or natural influences acting periodically. There are many others, which within the strict limits of health may cause such a condition of the brain as to produce sleep.

Authors, in considering sleep, have not always drawn the proper distinction between the exciting and the immediate cause. Thus Macario,[5] in alluding to the alleged causes of sleep, says:

“Among physiologists some attribute it to a congestion of blood in the brain; others to a directly opposite cause, that is, to a diminished afflux of blood to this organ; some ascribe it to a loss of nervous fluid, others to a flow of this fluid back to its source; others again find the cause in the cessation of the motion of the cerebral fibers, or rather in a partial motion in these fibers. Here I stop, for I could not, even if I wished, mention all the theories which have prevailed relative to this subject. I will only add that, in my opinion, the most probable proximate and immediate cause appears to be feebleness. What seems to prove this view is the fact that exhaustive hot baths, heat, fatigue, too great mental application are among the means which produce sleep.”

Undoubtedly the influence mentioned by Macario, and many others which he might have cited, lead to sleep. They do so through the medium of the nervous system—causing a certain change to take place in the physical condition of the brain. We constantly see instances of this transmission of impressions and the production of palpable effects. Under the influence of fatigue, the countenance becomes pale; through the actions of certain emotions, blushing takes place. When we are anxious or suffering or engaged in intense thought, the perspiration comes out in big drops on our brows; danger makes some men tremble, grief causes tears to flow. Many other examples will suggest themselves to the reader. It is surely, therefore, no assumption to say that certain mental or physical influences are capable of inducing such an alteration in the state of the brain as necessarily to cause sleep. These influences or exciting causes I propose to consider in detail, after having given my views relative to the condition of the brain which immediately produces sleep.

It is well established as regards other viscera, that during a condition of activity there is more blood in their tissues than while they are at rest. It is strange, therefore, that, relative to the brain, the contrary doctrine should have prevailed so long, and that even now, after the subject has been so well elucidated by exact observation, it should be the generally received opinion that during sleep the cerebral tissues are in a state approaching congestion. Thus Dr. Marshall Hall,[6] while contending for this view, also advances the theory that there is a special set of muscles, the duty of which is, by assuming a condition of tonic contraction, so to compress certain veins as to prevent the return of the blood from the heart.

Dr. Carpenter[7] is of the opinion that the first cause of sleep in order of importance is the pressure exerted by distended blood-vessels upon the encephalon.

Sir Henry Holland[8] declares that a “degree of pressure is essential to perfect and uniform sleep.”

Dr. Dickson[9] regards an increased determination of blood to the cerebral mass, and its consequent congestion in the larger vessels of the brain, as necessary to the induction of sleep.

In his very excellent work on Epilepsy, Dr. Sieveking[10] says:

“Whether or not there is actually an increase in the amount of blood in the brain during sleep, and whether, as has been suggested, the choroid plexuses become turgid or not, we are unable to affirm otherwise than hypothetically; the evidence is more in favor of cerebral congestion than of the opposite condition inducing sleep—evidence supplied by physiology and pathology.” Dr. Sieveking does not, however, state what this evidence is.

Barthez[11] is of the opinion that during sleep there is a general plethora of the smaller blood-vessels of the whole body. He does not appear to have any definite views relative to the condition of the cerebral circulation.

Cabanis[12] declares that as soon as the necessity for sleep is experienced, there is an increased flow of blood to the brain.

To come to more popular books than those from which we have quoted, we find Mr. Lewes,[13] when speaking of the causes of sleep, asserting that: “It is caused by fatigue, because one of the natural consequences of continued action is a slight congestion; and it is the congestion which produces sleep. Of this there are many proofs.” Mr. Lewes omits to specify these proofs.

Macnish[14] holds the view that sleep is due to a determination of blood to the head.

That a similar opinion has prevailed from very ancient times, it would be easy to show. I do not, however, propose to bring forward any further citations on this point, except the following, from a curious old black-letter book now before me, in which the views expressed, though obscure, are perhaps as intelligible as many met with in books of our own day:

“And the holy scripture in sundrie places doth call death by the name of sleepe, which is meant in respect of the resurrection; for, as after sleepe we hope to wake, so after death we hope to rise againe. But that definition which Paulus Ægineta maketh of sleepe, in my judgment, is most perfect where he saith: Sleepe is the rest of the pores animall, proceeding of some profitable humour moistening the braine. For here is shewed by what means sleepe is caused; that is, by vapours and fumes rising from the stomache to the head, where through coldness of the braine they being congealed, doe stop the conduites and waies of the senses, and so procure sleepe, which thing may plainly be perceived hereby; for that immediately after meate we are most prone to sleepe, because then the vapours ascende most abundantly to the braine, and such things as be most vaporous do most dispose to sleepe, as wine, milke, and such like.”[15]

The theory that sleep is due directly to pressure of blood-vessels, filled to repletion, upon the cerebral tissues, doubtless originated in the fact that a comatose condition may be thus induced. This fact has long been known. Servetus, among other physiological truths, distinctly announces it in his Christianismi Restitutio, when he says:

“Et quando ventriculi ita opplentur pituita, ut arteriæ ipsæ choroidis ea immergantur, tunc subito generatur appoplexia.”

Perhaps the theory which prevails at present, of sleep being due to the pressure of distended blood-vessels upon the choroid plexus, is derived from these words of Servetus.

That stupor may be produced by pressure upon the brain admits of no doubt. It is familiarly known to physicians, surgeons, and physiologists; the two former meet with instances due to pathological causes every day, and the latter bring it on at will in their laboratories. But this form of coma and sleep are by no means identical. On the contrary, the only point of resemblance between the two consists in the fact that both are accompanied by a loss of volition. It is true, we may often arrive at a correct idea of a physiological process from determining the causes and phenomena of its pathological variations, but such a course is always liable to lead to great errors, and should be conducted with every possible precaution. In the matter under consideration it is especially of doubtful propriety, for the reason stated, that coma is not to be regarded as a modification of sleep, but as a distinct morbid condition. Sir T. C. Morgan,[16] in alluding to the fact that sleep has been ascribed to a congested state of the brain, for the reason that in apoplectic stupor the blood-vessels of that organ are abnormally distended, objects to the theory, on the ground that it assimilates a dangerous malady to a natural and beneficial process. He states (what was true at the time he wrote) that the condition of the circulation through the brain, during sleep, is wholly unknown.

It is important to understand clearly the difference between stupor and sleep, and it is very certain that the distinction is not always made by physicians; yet the causes of the two conditions have almost nothing in common, and the phenomena of each are even more distinct.

1. In the first place, stupor never occurs in the healthy individual, while sleep is a necessity of life.

2. It is easy to awaken a person from sleep, while it is often impossible to arouse him from stupor.

3. In sleep the mind may be active, in stupor it is as it were dead.

4. Pressure upon the brain, intense congestion of its vessels, the circulation of poisoned blood through its substance cause stupor, but do not induce sleep. For the production of the latter condition a diminished supply of blood to the brain, as will be fully shown hereafter, is necessary.

Perhaps no one agent so distinctly points out the difference between sleep and stupor as opium and its several preparations. A small dose of this medicine acting as a stimulant increases the activity of the cerebral circulation, and excites a corresponding increase in the rapidity and brilliancy of our thoughts. A larger dose lessens the amount of blood in the brain, and induces sleep. A very large dose sometimes diminishes the power of the whole nervous system, lessens the activity of the respiratory function, and hence allows blood which has not been properly subjected to the influence of the oxygen of the atmosphere to circulate through the vessels of the brain. There is nothing in the opium itself which produces excitement, sleep, or stupor, by any direct action upon the brain. All its effects are due to its influence on the heart and blood-vessels, through the medium, however, of the nervous system. This point can be made plainer by adducing the results of some experiments which I have lately performed.

Experiment.—I placed three dogs of about the same size under the influence of chloroform, and removed from each a portion of the upper surface of the skull an inch square. The dura mater was also removed, and the brain exposed. After the effects of the chloroform had passed off—some three hours subsequent to the operation—I administered to number one the fourth of a grain of opium, to number two a grain, and to number three two grains. The brain of each was at the time in a perfectly natural condition.

At first the circulation of the blood in the brain was rendered more active, and the respiration became more hurried. The blood-vessels, as seen through the openings in the skulls, were fuller and redder than before the opium was given, and the brain of each animal rose through the hole in the cranium. Very soon, however, the uniformity which prevailed in these respects was destroyed. In number one the vessels remained moderately distended and florid for almost an hour, and then the brain slowly regained its ordinary appearance. In number two the active congestion passed off in less than half an hour, and was succeeded by a condition of very decided shrinking, the surface of the brain having fallen below the surface of the skull, and become pale. As these changes supervened, the animal gradually sank into a sound sleep, from which it could easily be awakened. In number three the surface of the brain became dark, almost black, from the circulation of blood containing a superabundance of carbon, and owing to diminished action of the heart and vessels it sank below the level of the opening, showing, therefore, a diminished amount of blood in its tissue. At the same time the number of respirations per minute fell from 26 to 14, and they were much weaker than before. A condition of complete stupor was also induced from which the animal could not be aroused. It persisted for two hours. During its continuance, sensation of all kind was abolished, and the power of motion was altogether lost.

It might be supposed that the conditions present in numbers two and three differed only in degree. That this was not the case is shown by the following experiment:

Experiment.—To the dogs two and three I administered on the following day, as before, one and two grains of opium respectively. As soon as the effects began to be manifested upon the condition of the brain, I opened the trachea of each, and, inserting the nozzle of a bellows, began the process of artificial respiration. In both dogs the congestion of the blood-vessels of the brain disappeared. The brain became collapsed, and the animals fell into a sound sleep, from which they were easily awakened. If the action of the bellows was stopped and the animals were left to their own respiratory efforts, no change ensued in number two, but in number three the surface of the brain became dark, and stupor resulted.

In order to be perfectly assured upon the subject, I proceeded as follows with another dog:

Experiment.—The animal was trephined as was the others, and five grains of opium given. At the same time the trachea was opened and the process of artificial respiration instituted. The brain became slightly congested, then collapsed, and sleep ensued. The sleep was sound, but the animal was easily awakened by tickling its ear. After I had continued the process for an hour and a quarter, I removed the nozzle of the bellows, and allowed the animal to breathe for itself. Immediately the vessels of the brain were filled with black blood, and the surface of the brain assumed a very dark appearance.

The dog could no longer be aroused, and died one hour and a quarter after the process was stopped.

I have only stated those points of the experiments cited which bear upon the subject under consideration, reserving for another occasion others of great interest. It is, however, shown that a small dose of opium excites the mind, because it increases the amount of blood in the brain; that a moderate dose causes sleep, because it lessens the amount of blood; and that a large dose produces stupor by impeding the respiratory process, and hence allowing blood loaded with carbon, and therefore poisonous, to circulate through the brain.

It is also shown that the condition of the brain during stupor is very different from that which exists during sleep. In the one case its vessels are loaded with dark blood; in the other they are comparatively empty, and the blood remains florid.

I think it will be sufficiently established, in the course of these remarks, that sleep is directly caused by the circulation of a less quantity of blood through the cerebral tissues than traverses them while we are awake. This is the immediate cause of healthy sleep. Its exciting cause is, as we have seen, the necessity for repair. The condition of the brain which is favorable to sleep may also be induced by various other causes, such as heat, cold, narcotics, anæsthetics, intoxicating liquors, loss of blood, etc. If these agents are allowed to act excessively, or others, such as carbonic oxide, and all those which interfere with the oxygenation of the blood, are permitted to exert their influence, stupor results.

The theory above enunciated, although proposed in a modified form by Blumenbach several years since, and subsequently supported by facts brought forward by other observers, has not been received with favor by any considerable number of physiologists. Before, therefore, detailing my own experience, I propose to adduce a few of the most striking proofs of its correctness which I have been able to collect, together with the opinions of some of those inquirers who have recently studied the subject from this point of view.

Blumenbach[17] details the case of a young man, eighteen years of age, who had fallen from an eminence and fractured the frontal bone, on the right side of the coronal suture. After recovery took place a hiatus remained, covered only by the integument. While the young man was awake this chasm was quite superficial, but as soon as sleep ensued it became very deep. The change was due to the fact that during sleep the brain was in a collapsed condition. From a careful observation of this case, as well as from a consideration of the phenomena attendant on the hibernation of animals, Blumenbach[18] arrives at the conclusion that the proximate cause of sleep consists in a diminished flow of oxygenated blood to the brain.

Playfair[19] thinks that sleep is due to “a diminished supply of oxygen to the brain.”

Dendy[20] states that there was, in 1821, at Montpellier, a woman who had lost part of her skull, and the brain and its membranes lay bare. When she was in deep sleep the brain remained motionless beneath the crest of the cranial bones; when she was dreaming it became somewhat elevated; and when she was awake it was protruded through the fissure in the skull.

Among the most striking proofs of the correctness of the view that sleep is due to diminished flow of blood to the head, are the experiments of Dr. Alexander Fleming,[21] late Professor of Medicine, Queen’s College, Cork. This observer states, that while preparing a lecture on the mode of operation of narcotic medicines, he conceived the idea of trying the effect of compressing the carotid arteries on the functions of the brain. The first experiment was performed on himself, by a friend, with the effect of causing immediate and deep sleep. The attempt was frequently made, both on himself and others, and always with success. “A soft humming in the ears is heard; a sense of tingling steals over the body, and in a few seconds complete unconsciousness and insensibility supervene, and continue so long as the pressure is maintained.”

Dr. Fleming adds, that whatever practical value may be attached to his observations, they are at least important as physiological facts, and as throwing light on the causes of sleep. It is remarkable that his experiments have received so little notice from physiologists.

Dr. Bedford Brown,[22] of North Carolina, has recorded an interesting case of extensive compound fracture of the cranium, in which the opportunity was afforded him of examining the condition of the cerebral circulation while the patient was under the influence of an anæsthetic, preparatory to the operation of trephining being performed. A mixture of ether and chloroform was used. Dr. Brown says:

“Whenever the anæsthetic influence began to subside, the surface of the brain presented a florid and injected appearance. The hemorrhage increased, and the force of the pulsation became much greater. At these times so great was the alternate heaving and bulging of the brain, that we were compelled to suspend operations until they were quieted by a repetition of the remedy. Then the pulsations would diminish, the cerebral surface recede within the opening of the skull, as if by collapse; the appearance of the organ becoming pale and shrunken with a cessation of the bleeding. In fact, we were convinced that diminished vascularity of the brain was an invariable result of the impression of chloroform or ether. The changes above alluded to recurred sufficiently often, during the progress of the operation, in connection with the anæsthetic treatment, to satisfy us that there could be no mistake as to the cause and effect.”

It will be shown, in the course of the present memoir, that Dr. Brown’s conclusions, though in the main correct, are erroneous so far as they relate to the effect of chloroform upon the cerebral circulation; nor does it appear that he employed this agent unmixed with ether, in the case which he has recorded so well. He has, probably, based his remarks on this point upon the phenomena observed when the compound of ether and chloroform was used—the action of pure chloroform, as regards its effect upon the quantity of blood circulating through the brain, being the reverse of that which he claims for it.

But the most philosophical and most carefully digested memoir upon the proximate cause of sleep, which has yet been published, is that of Mr. Durham.[23] Although my own experiments in the same direction, and which will be hereafter detailed, were of prior date, I cheerfully yield all the honor which may attach to the determination of the question under consideration to this gentleman, who has not only worked it out independently, but has anticipated me several years in the publication, besides carrying his researches to a much further point than my own extended.

With the view of ascertaining by ocular examination the vascular condition of the brain during sleep, Durham placed a dog under the influence of chloroform, and removed with a trephine a portion of bone as large as a shilling from the parietal region; the dura mater was also cut away. During the continuance of the anæsthetic influence, the large veins of the surface of the pia mater were distended, and the smaller vessels were full of dark-colored blood. The longer the administration of the chloroform was continued, the greater was the congestion. As the effects of this agent passed off, the animal sank into a natural sleep, and then the condition of the brain was very materially changed. Its surface became pale and sank down below the level of the bone; the veins ceased to be distended, and many which had been full of dark blood could no longer be distinguished. When the animal was roused, the surface of the brain became suffused with a red blush, and it ascended into the opening through the skull. As the mental excitement increased, the brain became more and more turgid with blood, and innumerable vessels sprang into sight. The circulation was also increased in rapidity. After being fed, the animal fell asleep, and the brain again became contracted and pale. In all these observations the contrast between the two conditions was exceedingly well marked.

To obviate any possible effects due to atmospheric pressure, watch-glasses were applied to the opening in the skull, and securely cemented to the edges with Canada balsam. The phenomena observed did not differ from those previously noticed; and, in fact, many repetitions of the experiment gave like results.

Durham, in the next place, applied ligatures to the jugular and vertebral veins, with the effect—as was to be expected—of producing intense congestion of the brain, attended with coma. This last condition he very properly separates from sleep, which is never caused by pressure from the veins. He likens sleep to the state induced by preventing the access of blood to the brain through the carotids, but does not allude to Fleming’s researches on this point.

From his observations, Durham deduces the following conclusions:

“1. Pressure of distended veins upon the brain is not the cause of sleep, for during sleep the veins are not distended; and when they are, symptoms and appearances arise which differ from those which characterize sleep.

“2. During sleep the brain is in a comparatively bloodless condition, and the blood in the encephalic vessels is not only diminished in quantity, but moves with diminished rapidity.

“3. The condition of the cerebral circulation during sleep is, from physical causes, that which is most favorable to the nutrition of the brain tissue; and, on the other hand, the condition which prevails during waking is associated with mental activity, because it is that which is most favorable to oxydation of the brain substance, and to various changes in its chemical constitution.

“4. The blood which is derived from the brain during sleep is distributed to the alimentary and excretory organs.

“5. Whatever increases the activity of the cerebral circulation tends to preserve wakefulness; and whatever decreases the activity of the cerebral circulation, and, at the same time, is not inconsistent with the general health of the body, tends to induce and favor sleep. Such circumstances may act primarily through the nervous or through the vascular system. Among those which act through the nervous system, may be instanced the presence or absence of impressions upon the senses, and the presence or absence of exciting ideas. Among those which act through the vascular system, may be mentioned unnaturally or naturally increased or decreased force or frequency of the heart’s action.

“6. A probable explanation of the reason why quiescence of the brain normally follows its activity, is suggested by the recognized analogical fact that the products of chemical action interfere with the continuance of the action by which they are produced.”

Luys,[24] after stating the two opposite views relative to the state of the cerebral circulation during sleep, gives his adhesion on principles of analogy to that which holds to a diminished afflux of blood. Taking the condition of the salivary glands during their periods of inaction as the basis of his argument, he says:

“We are then naturally led, in making the application of known facts to those which are yet unknown, to say that the nervous tissue and the glandular tissue present, between themselves, the closest analogy, so far as circulatory phenomena and the double alternation of their periods of activity and repose are concerned. And that if the period during which the gland reconstitutes its immediate principles corresponds to a period of reduced activity of circulatory phenomena—to a state of relative anæmia—and that when it functionates it is awakened to a state in which its capillaries are turgid with blood, it is very admissible that the same circulatory conditions should be present in the nervous tissue, and that the period of inactivity, or of sleep, should be characterized by an anemic state. Inversely, the period of activity or wakefulness should be marked by an acceleration of the flow of blood, and by a kind of erethism of the vascular element.”

Having thus, in as succinct a manner as possible, brought forward the principal observations relative to the immediate cause of sleep, which up to the present time have been published, I come, in the next place, to detail the result of my own researches.

In 1854 a man came under my observation who had, through a frightful railroad accident, lost about eighteen square inches of his skull. There was thus a fissure of his cranium three inches wide and six inches long. The lost portion consisted of a great part of the left parietal, and part of the frontal, occipital, and right parietal bones. The man, who was employed as a wood chopper, was subject to severe and frequent epileptic fits, during which I often attended him. In the course of my treatment, I soon became acquainted with the fact that, at the beginning of the comatose condition which succeeded the fits, there was invariably an elevation of that portion of the scalp covering the deficiency in the cranium. As the stupor passed away, and sleep from which he could easily be aroused ensued, the scalp gradually became depressed. When the man was awake, the region of scalp in question was always nearly on a level with the upper surface of the cranial bones. I also noticed on several occasions that during natural sleep the fissure was deeper, and that in the instant of awaking, the scalp covering it rose to a much higher level.

After my attention was thus drawn to this subject, I observed that in young infants the portion of scalp covering the anterior fontanelle was always depressed during sleep, and elevated during wakefulness.

During the summer of 1860 I undertook a series of experiments, with the view of ascertaining the condition of the cerebral circulation during sleep, of which the following is a brief abstract:

A medium-sized dog was trephined over the left parietal bone, close to the sagittal suture, having previously been placed under the full anæsthetic influence of ether. The opening made by the trephine was enlarged with a pair of strong bone-forceps, so as to expose the dura mater to the extent of a full square inch. This membrane was then cut away and the brain brought into view. It was sunk below the inner surface of the skull, and but few vessels were visible. Those which could be perceived, however, evidently conveyed dark blood, and the whole exposed surface of the brain was of a purple color. As the anæsthetic influence passed off, the circulation of the blood in the brain became more active. The purple hue faded away, and numerous small vessels filled with red blood became visible; at the same time the volume of the brain increased, and when the animal became fully aroused, the organ protruded through the opening in the skull to such an extent that, at the most prominent part, its surface was more than a quarter of an inch above the external surface of the cranium. While the dog continued awake, the condition and position of the brain remained unchanged. After the lapse of half an hour, sleep ensued. While this state was coming on I watched the brain very attentively. Its volume slowly decreased; many of its smaller blood-vessels became invisible, and finally it was so much contracted that its surface, pale and apparently deprived of blood, was far below the level of the cranial wall.

Two hours subsequently the animal was again etherized, in order that the influence of the ether upon the cerebral circulation might be observed from the commencement. At the time the dog was awake, and had a few minutes previously eaten a little meat and drank a small quantity of water. The brain protruded through the opening in the skull, and its surface was of a pink hue, with numerous red vessels ramifying over it. The ether was administered by applying to the muzzle of the animal a towel folded into the shape of a funnel, and containing a small sponge saturated with the agent.

As soon as the dog commenced to inspire the ether, the appearance of the brain underwent a change of color, and its volume became less. As the process of etherization was continued, the color of the surface darkened to a deep purple, and it ceased to protrude through the opening. Finally, when a state of complete anæsthesia was reached, it was perceived that the surface of the brain was far below the level of the cranial fissure, and that its vessels conveyed black blood alone.

Gradually the animal regained its consciousness; the vessels resumed their red color, and the brain was again elevated to its former position. In this last experiment there did not appear to be any congestion of the brain. Had this condition existed, it would have been difficult to account for the diminution in bulk, which certainly took place. There was evidently less blood in the cerebral tissue than there had been previously at the etherization; but this blood, instead of being oxygenated, was loaded with excrementitial matters, and consequently was not fitted to maintain the brain in a condition of activity.

The following morning, the dog being quite lively, I removed the sutures which had been placed in the skin, covering the hole in the cranium, with the view of ascertaining the effects of chloroform upon the brain, when introduced into the system by inhalation. Suppuration had not yet taken place, and the parts were in good condition. The opening in the skull was completely filled by the brain, and the surface of the latter was traversed by a great many small vessels carrying red blood. The chloroform was administered in the same way in which the ether had been given the previous day.

In a few seconds the change in color of the blood circulating in the vessels began to take place, but there was no sinking of the brain below the level of the chasm in the skull. On the contrary, its protrusion was greater than before the commencement of the experiment. There was thus not only unoxygenated blood circulating to too great an extent through the brain, but there was very decided congestion.

The foregoing experiments were frequently repeated on other dogs, and also on rabbits, with like results. Within a short period I have in part gone over the ground again, without observing any essential point of difference in the effects produced.

I have never repeated Fleming’s experiment on the human subject, except in one instance, and then sleep, or a condition resembling it, was instantaneously produced. As soon as the pressure was removed from the carotids, the individual gained his consciousness. On dogs and rabbits, however, I have performed it frequently, and though if the pressure be continued for longer than one minute, convulsions generally ensue, a state of insensibility resembling natural sleep is always the first result. Lately, I have had, through the kindness of my friend, Dr. Van Buren, the opportunity of examining a case which affords strong confirmation of the correctness of the preceding views. It was that of a lady in whom both common carotids were tied for a cirsoid aneurism, involving a great portion of the right side of the scalp. One carotid was tied by the late Dr. J. Kearney Rogers, and the other by Dr. Van Buren, seven years ago, with the effect of arresting the progress of the disease. No peculiar symptoms were observed in consequence of these operations, except the supervention of persistent drowsiness, which was especially well marked after the last operation, and which, even now, is at times quite troublesome.

We thus see that the immediate cause of sleep is a diminution of the quantity of blood circulating in the vessels of the brain, and that the exciting cause of periodical and natural sleep is the necessity which exists that the loss of substance which the brain has undergone, during its state of greatest activity, should be restored. To use the simile of the steam-engine again, the fires are lowered and the operatives go to work to repair damages and put the machine in order for next day’s work.

Whatever other cause is capable of lessening the quantity of blood in the brain is also capable of inducing sleep. There is no exception to this law, and hence we are frequently able to produce this condition at will. Several of these factors have been already referred to, but it will be interesting to consider them all somewhat more at length.

Heat.—Most persons in our climate, and in those of higher temperatures, have felt the influence of heat in causing drowsiness, and eventually sleep, if the action is powerful enough and sufficiently prolonged. It is not difficult to understand the mode by which heat acts in giving rise to sleep. During the prevalence of high temperatures the blood flows in increased proportion to the surface of the body and to the extremities, and consequently the quantity in the brain is diminished. Sleep accordingly results unless the irritation induced by the heat is so great as to excite the nervous system. Heat applied directly to the head exerts, of course, a directly contrary effect upon the cerebral circulation, as we see in sun-stroke. Here there is internal cerebral congestion, loss of consciousness, stupor, etc.

That the effect of heat is to dilate the vessels of the part subjected to its influence, can be ascertained by putting the arm or leg into hot water. The swelling of the blood-vessels is then very distinctly seen. It will be shown hereafter that one of the best means of causing sleep in morbid wakefulness is the warm-bath.

Cold.—A slight degree of cold excites wakefulness at first, but if the constitution be strong the effect is to predispose to sleep. This it does by reason of the determination of blood to the surface of the body which moderate cold induces in vigorous persons. The ruddy complexion and warmth of the hands and feet produced in such individuals under the action of this influence are well known.

But if the cold be very intense, or the reduction of temperature sudden, the system, even of the strongest persons, cannot maintain a resistance, and then a very different series of phenomena result. Stupor, not sleep, is the consequence. The blood-vessels of the surface of the body contract and the blood accumulates in the internal organs, the brain among them. Many instances are on record showing the effect of extreme cold in producing stupor and even death. One of the most remarkable of these is that related by Captain Cook, in regard to an excursion of Sir Joseph Banks, Dr. Solander, and nine others, over the hills of Terra del Fuego. Dr. Solander, knowing from his experience in Northern Europe that the stupor produced by severe cold would terminate in death unless resisted, urged his companions to keep in motion when they began to feel drowsy. “Whoever sits down will sleep,” said he, “and whoever sleeps will rise no more.” Yet he was the first to feel this irresistible desire for repose, and entreated his companions to allow him to lie down. He was roused from his stupor with great difficulty and carried to a fire, when he revived. Two black men of the party, whose organizations were not so robust as those of the whites, perished. Dr. Whiting[25] relates the case of Dr. Edward Daniel Clark, the celebrated traveler, who on one occasion came very near losing his life by cold. He had performed divine service at a church near Cambridge, and was returning home on horseback, when he felt himself becoming very cold and sleepy. Knowing the danger of yielding to the influence which was creeping over him, he put his horse into a fast trot, hoping thereby to arouse himself from the alarming torpor. This means proving unavailing, he got down and led his horse, walking as fast as he could. This, however, did not long succeed. The bridle dropped from his arm, his legs became weaker and weaker, and he was just sinking to the ground when a gentleman who knew him came up in a carriage and rescued him.

I have often myself noticed this effect of cold in producing numbness and drowsiness, and on one occasion was nearly overcome by it. I was crossing the mountain ridge between Cebolleta and Covero, in New Mexico, when the thermometer fell in about two hours from 52° to 22° Fahrenheit. So great was the effect upon me that if I had had much farther to go I should probably have succumbed. As it was, I reached a rancho in time to be relieved, though several minutes elapsed before I was able to speak. The sensations experienced were rather agreeable than otherwise. There was a great desire to rest and to yield to the languor which was present, and there was a feeling of recklessness which rendered me perfectly indifferent to the consequences. I should have dismounted from my horse and given way to the longing for repose if I had been able to do so. I have several times experienced very similar effects from change of air. A few years since I was so drowsy at the sea-coast, whither I had gone from a hot city, that it was with difficulty I could keep awake, even when engaged in active physical exercise.

Another potent cause of sleep, and one of which we generally avail ourselves, is the diminution of the power of the attention. To bring this influence into action generally requires only the operation of the will under circumstances favorable to the object in view. Shutting the eyes so as to exclude light, getting beyond the sound of noises, refraining from the employment of the other senses, and avoiding thought of all kind, will generally, when there is no preventing cause, induce sleep. To think, and to maintain ourselves in connection with the outward world by means of our senses requires that the circulation of blood in the brain shall be active. When we isolate ourselves from external things, and restrain our thoughts, we lessen the amount of blood in the brain, and sleep results. It is not, however, always easy for us to do this. The nervous system is excited, ideas follow each other in rapid succession, and we lie awake hour after hour vainly trying to forget that we exist. The more the will is brought to bear upon the subject the more rebellious is the brain, and the more it will not be forced by such means into a state of quietude. We must then either let it run riot till it is worn out by its extravagancies, or we must fatigue it by requiring it to perform labor which is disagreeable. Just as we might do with an individual of highly destructive propensities, who was going about pulling down his neighbors’ houses. We might, if we were altogether unable to stop him, let him alone till he had become thoroughly wearied with his exertions, or we might divert him from his plan by guiding him to some tough piece of work which would exhaust his strength sooner than would his original labor.

Many ways of thus tiring the brain have been proposed. The more irksome they are, the more likely they are to prove effectual. Counting a hundred backward many times, listening to monotonous sounds, thinking of some extremely disagreeable and tiresome subject, with many other devices, have been suggested, and have proved more or less effectual. Boerhaave[26] states that he procured sleep by placing a brass pan in such a position that the patient heard the sound of water which was made to fall into it, drop by drop. In general terms, monotony predisposes to sleep. Dr. Dickson[27] quotes Southey’s experience as related in the Doctor,[28] and I also cannot do better than lay it before the reader, particularly as it indicates several methods which may be more efficacious with others than the one he found to succeed so admirably.

“I put my arms out of bed; I turned the pillow for the sake of applying a cold surface to my cheek; I stretched my feet into the cold corner; I listened to the river and to the ticking of my watch; I thought of all sleepy sounds and of all soporific things—the flow of water, the humming of bees, the motion of a boat, the waving of a field of corn, the nodding of a mandarin’s head on the chimney-piece, a horse in a mill, the opera, Mr. Humdrum’s conversations, Mr. Proser’s poems, Mr. Laxative’s speeches, Mr. Lengthy’s sermons. I tried the device of my own childhood, and fancied that the bed rushed with me round and round. At length Morpheus reminded me of Dr. Torpedo’s Divinity Lectures, where the voice, the manner, the matter, even the very atmosphere and the streamy candlelight were all alike somnific; when he who, by strong effort, lifted up his head and forced open the reluctant eyes never failed to see all around him asleep. Lettuces, cowslip wine, poppy syrup, mandragora, hop pillows, spider’s web pills, and the whole tribe of narcotics, up to bang and the black-drop, would have failed,—but this was irresistible; and thus, twenty years after date, I found benefit from having attended the course.”

Frequently the power of the attention is diminished by natural causes. After the mind has been strained a long time in one particular direction, and during which period the brain was doubtless replete with blood, the tension is at last removed, the blood flows out of the brain, the face becomes pale, and sleep ensues. It is thus, as Macnish[29] says, that “the finished gratification of all ardent desires has the effect of inducing slumber; hence after any keen excitement the mind becomes exhausted and speedily relapses into this state.”

A gentleman recently under my care for a paralytic affection, informed me that he could at any time render himself sleepy by looking for a few minutes at a bright light, so as to fatigue the eyes, or by paying particular attention to the noises in the street, so as to weary the sense of hearing. It is well known that sleep may be induced by gentle frictions of various parts of the body, and doubtless the other senses are capable of being so exhausted, if I may use the expression, as to diminish the power of the attention, and thus lessen the demand for blood in the brain. As a consequence, sleep ensues.

The cutting off of sensorial impressions aids in lessening the power of the attention and thus predisposes to sleep. Stillness, darkness, the absence of any decided impression on the skin, and the nonexistence of odors and flavors, accomplish this end. In these respects, however, habit exercises great influence, and thus individuals, for instance, who are accustomed to continual loud noises, cannot sleep when the sound is interrupted. As we have already seen, however, the predisposition to sleep is, in healthy persons, generally so great that when it has been long resisted, no sensation, however strong it may be, can withstand its power.

Digestion leads to sleep by drawing upon the brain for a portion of its blood. It is for this reason that we feel sleepy after the ingestion of a hearty dinner. A lady of my acquaintance is obliged to sleep a little after each meal. The desire to do so is irresistible; her face becomes pale; her extremities cold; and she sinks into a quiet slumber, which lasts fifteen or twenty minutes. In this lady the amount of blood is not sufficient for the due performance of all the operations of the economy. The digestive organs imperatively require an increased quantity, and the flow takes place from the brain; it being the organ with her which can best spare this fluid. As a rule, persons who eat largely, and have good digestive powers, sleep a great deal, and many persons are unable to sleep at night till they have eaten a substantial supper. The lower animals generally sleep after feeding, especially if the meal has been large.

Excessive loss of blood produces sleep. We can very readily understand why this should be so if we adopt the theory which has been supported in the foregoing pages. It would be exceedingly difficult to explain the fact upon any other hypothesis. I have seen many instances of somnolency due to this cause. It acts not only by directly lessening the quantity of blood in the brain, but also by so enfeebling the heart’s action as to prevent a due supply of blood being sent to the cerebral vessels.

Debility is almost always accompanied by a disposition to inordinate sleep. The brain is one of the first organs to feel the effects of a diminished amount of blood or a depraved quality of this fluid being supplied, and hence, in old age, or under the influence of a deficient quantity of food, or through the action of some exhausting disease, there is generally more sleep than when the physical health is not deteriorated.

The action of certain medicines, and of other measures capable of causing sleep, not coming within the range of ordinary application, will be more appropriately considered hereafter.

CHAPTER III.

THE PHYSICAL PHENOMENA OF SLEEP.

The approach of sleep is characterized by a languor which is agreeable when it can be yielded to, but which, when circumstances prevent this, is far from being pleasant. Many persons are rendered irritable as soon as they become sleepy, and children are especially liable to manifest ill temper under the uncomfortable feelings they experience when unable to indulge the inclination to sleep. It is somewhat difficult to analyze the various phenomena which go to make up the condition called sleepiness. The most prominent feelings are an impression of weight in the upper eyelids, and of a general relaxation of the muscles of the body, but there is besides an internal sensation of supineness, enervation, and torpor, to describe which is by no means easy. This sluggishness is closely allied in character if not altogether identical with that experienced before an attack of fainting, and is doubtless due to a like cause—a deficient quantity of blood in the brain. Along with this languor there is a general obtuseness of all the senses, which increases the separation of the mind from the external world, already initiated by the physical condition of the brain. The liveliest scenes cease to engage the attention, and the most exciting conversation no longer interests. For a time, indeed, such circumstances may dissipate the inclination for sleep, but eventually nature obtains the ascendency and consciousness is lost. Before this event there is usually yawning—a phenomenon strongly indicative of a wearied attention; the head nods and droops upon the breast, and the body assumes that position which is most conducive to ease, comfort, and entire muscular inactivity.

The order in which the muscles lose their power is in general well marked, and bears a distinct relation, as Cabanis[30] has pointed out, to the importance of their functions. Thus, the muscles which move the arms and legs become relaxed before those which support the head, and the latter before those which maintain the erectness of the back. This, however, is not always the case, for, as we have already seen, individuals will occasionally walk, and keep their position on horseback, while in a sound sleep, and all of us have seen persons slumbering in church, their heads dropping on their breasts, but yet firmly holding their prayer-books in their hands under the pretense of going through the services.

As regards the senses, the sight is of course the first to be lost in ordinary cases—the closure of the eyelids interposing a physical obstruction to the entrance of light. Even when the eyelids have been removed, or from disease cannot be closed, the sight, nevertheless, is the first of the special senses to be abolished. Some animals, as the hare for example, do not shut the eyes when asleep; but even in them the ability to see disappears before the action of the other senses is suspended.

These latter are not altogether abolished during sleep; their acuteness is simply lessened. Taste is the first to fade, and then the smell; hearing follows, and touch yields last of all, and is most readily re-excited. To awake a sleeping person, impressions made upon the sense of touch are more effectual than attempts to arouse through any of the other senses; the hearing comes next in order, smell next, then taste, and the sight is the last of all in capacity for excitation.

During sleep the respiration is slower, deeper, and usually more regular than during wakefulness. The vigor of the process is lessened, and therefore there is a diminution of the pulmonary exhalations. In all probability, also, the ciliated epithelium which lines the air-passages functionates with reduced activity. Owing to this circumstance and to the general muscular torpor which prevails, mucus accumulates in the bronchial tubes and requires to be expectorated on awaking.

The circulation of the blood is rendered slower. The heart beats with more regularity, but with diminished force and frequency. As a consequence the blood is not distributed to distant parts of the body so thoroughly and rapidly as during wakefulness, and accordingly the extremities readily lose their heat. Owing to the reduction in the activity of the respiratory and circulatory functions, the temperature of the whole body falls, and coldness of the atmosphere is less easily resisted.

The functions of the several organs concerned in digestion have their activity increased by sleep. The blood which leaves the brain, goes, as Durham has shown, to the stomach and other abdominal viscera, and hence the quantities of the digestive juices are augmented, and the absorption of the nutritious elements of the food is promoted.

The urine is excreted in less quantity during sleep than when the individual is awake and engaged in mental or physical employment, because the wear and tear of the system is at its minimum.

The perspiration is likewise reduced in amount by sleep. In warm weather, however, the effort to go to sleep often causes an increase in the quantity of this excretion, just as would any other mental or bodily exertion. This circumstance has led some writers to a conclusion the reverse of that just expressed. Others, again, have accepted the doctrine of Sanctorius on this point without stopping to inquire into its correctness. This author,[31] among other aphorisms relating to sleep, gives the following:

“Undisturbed sleep is so great a promoter of perspiration, that in the space of seven hours, fifty ounces of the concocted perspirable matter do commonly exhale out of strong bodies.

“A man sleeping the space of seven hours is wont, insensibly, healthfully, and without any violence, to perspire twice as much as one awake.”

The observations of Sanctorius with his weighing chair led to a good many important results, but they were inexact so far as the function of the skin was concerned, in that they made no division between the loss by this channel and that which takes place through the lungs, for by perspiration in the above quotations he means not only the exhalation from the skin, but the products of respiration—aqueous vapor, carbonic acid, etc. His apparatus was, besides, very imperfect, and could not possibly have given the delicate indications which the subject requires.

Whether the condition of sleep promotes the absorption of morbid growths and accumulations of fluids is very doubtful. Macnish[32] contends that it does, but a priori reasoning would rather lead us to an opposite conclusion. Deficiencies are probably more rapidly made up during sleep than during wakefulness, and thus ulcers heal with more rapidity, owing to the increased formation of granulations which takes place; but the removal of tumors, etc. by natural process involves the operation of forces the very opposite of those concerned in reparation, and observation teaches us that sleep is a condition peculiarly favorable to the deposition of the materials constituting morbid growths. Some writers have alleged that sleep accelerates the absorption of dropsical effusions, but the disappearance of such accumulations during the condition in question is clearly due to the mechanical causes depending upon the position of the body.

It has also been asserted that there is an exaltation of the sexual feeling during sleep. It is difficult to arrive at any very definite conclusion on this point, but it is probable that here again the position of the body conjoined with the heat of the bed has much to do in producing the erotic manifestations occasionally witnessed. Every physician who has had much to do with cases of the kind knows that sleeping upon the back, by which means the blood gravitates to the generative organs and to the lower part of the spinal cord, will often give rise to seminal emissions with or without erotic dreams, and that such occurrences may generally be prevented by the individual avoiding the dorsal decubitus and resting upon one side or the other while asleep. The erections which the generality of healthy men experience in the morning before rising from bed are likewise due to the fact that the recumbent posture favors the flow of blood to the penis and testicles. Such erections are usually unaccompanied by venereal desire.

The ganglionic nervous system and the spinal cord continue in action during sleep, though generally with somewhat diminished power and sensibility. The reflex faculty of the latter organ is still maintained, and thus various movements are executed without the consciousness of the brain being awakened. Somnambulism is clearly a condition of exaltation in the functions of the spinal cord without the controlling influence of the cerebrum being brought into action. But, aside from this rather abnormal phenomenon, there are others which are entirely within the range of health, and which show that the spinal cord is awake, even though the sleep be most profound. Thus, for instance, if the position of the sleeper becomes irksome, it is changed; if the feet become cold, they are drawn up to a warmer part of the bed; and cases are recorded in which individuals have risen from bed and emptied a distended bladder without awaking.

The instances brought forward in a previous chapter of persons riding on horseback and walking during sleep show the activity of the spinal cord, and not that the will is exercised; and Cabanis[33] is wrong in the view which he gives of such phenomena in the following extract.

Speaking of cases like those just referred to, he says:

“These rare instances are not the only ones in which movements are observed produced during sleep by that portion of the will which is awake; for it is by virtue of certain direct sensations that a sleeping man moves his arm to brush away the flies from his face, that he draws the cover around him so as to envelop himself carefully, or that he turns in bed till he has found a comfortable position. It is the will which during sleep maintains the contraction of the sphincter of the bladder, notwithstanding the effort of the urine to escape.”

Such examples as the above we now know to be instances of reflex action, and as not, therefore, being due to the exercise of the will.

Sleep favors the occurrence of certain pathological phenomena. Thus individuals affected with hæmorrhoids have the liability to hemorrhage increased when they are asleep. Several instances of the kind have come under my notice. In one the patient lost so large a quantity of blood that syncope ensued and might have terminated fatally had not his condition been accidentally discovered. Bleeding from the lungs is also more apt to occur during sleep in those who are predisposed to it. Darwin states that a man of about fifty years of age, subject to hæmorrhoids, was also attacked with hæmoptysis three consecutive nights at about the same hour—two o’clock—being awakened thereby from a state of very profound sleep. He was advised to suffer himself to be roused at one o’clock, and to leave his bed at that hour. He did so with the result not only of entirely breaking up the hemorrhagic disposition, but also of curing himself of very violent attacks of headache, to which he had been subject for many years.

Epileptic fits are also more liable to occur during sleep than at other times, a fact not always susceptible of easy explanation. In a case of epilepsy now under my charge, this proclivity is so well marked that the patient, a lady, scarcely ever goes to sleep without being attacked. Her face becomes exceedingly pale just before the fit, and if then seen the paroxysm can be entirely prevented by waking her. She is never attacked at other times, and I am trying, with excellent results thus far, the plan of making her sleep altogether during the day and of waking her as soon as her face becomes pallid. It is probable that the fits in her case are due to a diminished amount of blood in the brain, and this supposition is strengthened by the additional fact that bromide of potassium—a substance which, as I have shown, lessens the amount of intracranial blood—invariably rendered her paroxysms more frequent and severe.

Sleep predisposes to attacks of gout in those who have the gouty diathesis, and likewise favors exacerbations in several other diseases which it is scarcely necessary to allude to specifically. The accession of fever toward night, and the increase which takes place in pain due to inflammation are generally associated with the approach of night, and have no direct relation with sleep.

Certain other morbid phenomena, such as somnambulism and nightmare, which have a necessary relation with sleep, will be more appropriately considered in another place.

On the other hand, sleep controls the manifestations of several diseases, especially those which are of a convulsive or spasmodic character. Thus the paroxysms of chorea cease during sleep, as do likewise the spasms of tetanus and hydrophobia. Headache is also generally relieved by sleep, though occasionally it is aggravated.

CHAPTER IV.

THE STATE OF THE MIND DURING SLEEP.

We have seen that though during sleep the operations of the senses are entirely suspended as regards the effects of ordinary impressions, the purely animal functions of the body continue in action. The heart beats, the lungs respire, the stomach, the intestines, and their accessory organs digest, the skin exhales vapor, and the kidneys secrete urine. With the central nervous system, however, the case is very different; for while some parts retain the property of receiving impressions or developing ideas, others have their actions diminished, exalted, perverted, or altogether arrested.

In the first place, there is, undoubtedly, during sleep, a general torpor of the sensorium, which prevents the appreciation of the ordinary excitations made upon the organs of the special senses. So far as the nerves themselves are concerned, there is no loss of their irritability or conducting power, and the impressions made upon them are, accordingly, perfectly well conveyed to the brain. The suspension of the operations of the senses is not therefore due to any loss of function in the optic nerve, the auditory nerve, the olfactory nerve, the gustatory nerve, or the cranial or spinal nerves concerned in the sense of touch, but solely to the inability of the brain to take cognizance of the impressions conveyed to it. In regard to the cause of this torpor, I have given my views in a previous chapter.

Now it must not be supposed that because mild excitations transmitted by the nerves of the special senses are incapable of making themselves felt, that therefore the brain is in a state of complete repose throughout all its parts. So far from such a condition existing, there are very decided proofs that several faculties are exercised to a degree almost equaling that reached during wakefulness, and we know that if the irritations made upon the senses be sufficiently strong, the brain does appreciate them, and the sleep is broken. This ability to be readily roused through the senses constitutes one of the main differences between sleep and stupor, upon which stress has been already laid.

Relative to the different faculties of the mind as affected by sleep, great variations are observed. It has been thought by some authors that several of them are really exalted above the standard attained during wakefulness, but this is probably a wrong view. The predominance which one or two mental qualities apparently assume is not due to any absolute exaggeration of power, but to the suspension of the action of other faculties, which, when we are not asleep, exercise a governing or modifying influence. Thus, for instance, as regards the imagination,—the faculty of all others which appears to be most increased,—we find, when we carefully study its manifestations in our own persons, that although there is often great brilliancy in its vagaries, that uncontrolled as it is by the judgment, the pictures which it paints upon our minds are usually incongruous and silly in the extreme. Even though the train of ideas excited by this faculty when we are asleep be rational and coherent, we are fully conscious on awaking that we are capable of doing much better by intentionally setting the brain in action and governing it by our will and judgment.

Owing to the fact that these two faculties of the mind are incapable of acting normally during sleep, the imagination is left absolutely without controlling influence. Indeed, we are often cognizant in those dreams which take place when we are half awake, of an inability to direct it. The impressions which it makes upon the mind are, therefore, intense, but of very little durability. Many stories are told of its power—how problems have been worked out, poetry and music composed, and great undertakings planned; but if we could get at the truth, we should probably find that the imagination of sleep had very little to do with the operations mentioned. Indeed, it is doubtful if the mind of a sleeping person can originate ideas. Those which are formed are, as Locke[34] remarks, almost invariably made up of the waking man’s ideas, and are for the most part very oddly put together; and we are all aware how commonly our dreams are composed of ideas, or based upon events which have recently occurred to us.

In the previous section to the one just quoted, Locke refers to the exaggeration of ideas which form so common a feature of our mental actions during sleep. “It is true,” he says, “we have sometimes instances of perception while we are asleep, and retain the memory of those thoughts; but how extravagant and incoherent for the most part they are, how little conformable to the perfection and order of a rational being, those acquainted with dreams need not be told.”

And yet many remarkable stories are related, which tend to show the high degree of activity possessed by the mind during sleep. Thus it is said of Tartini,[35] a celebrated musician of the eighteenth century, that one night he dreamed he had made a compact with the devil, and bound him to his service. In order to ascertain the musical abilities of his servitor, he gave him his violin, and commanded him to play a solo. The devil did so, and performed so admirably that Tartini awoke with the excitement produced, and seizing his violin, endeavored to repeat the enchanting air. Although he was unable to do this with entire success, his efforts were so far effectual that he composed one of the most admired of his pieces, which in recognition of its source he called the “devil’s sonata.”

Coleridge gives the following account of the composition of the fragment, Kubla Khan:

“In the summer of 1797, the author, then in ill health, had retired to a lonely farm-house, between Perlock and Linton, on the Exmoor confines of Somerset and Devonshire. In consequence of a slight indisposition, an anodyne had been prescribed, from the effects of which he fell asleep in his chair at the moment that he was reading the following sentence, or words of the same substance, in Purchas’s Pilgrimage: ‘Here the Khan Kubla commanded a palace to be built, and a stately garden thereunto. And thus ten miles of fertile ground were inclosed with a wall.’ The author continued for about three hours in a profound sleep, at least of the external senses, during which time he had the most vivid confidence that he could have composed not less than from two to three hundred lines, if that, indeed, can be called composition, in which all the images rose up before him as things with a parallel production of the corresponding expression without any sensation or consciousness of effort. On awaking, he appeared to himself to have a distinct recollection of the whole; and taking his pen, ink, and paper, instantly and eagerly wrote down the lines that are here preserved. At this moment he was unfortunately called out by a person on business from Perlock, and detained by him above an hour; and on his return to his room, found to his no small surprise and mortification, that though he still retained some vague and dim recollection of the general purport of the vision, yet with the exception of some eight or ten scattered lines and images, all the rest had passed away like the images on the surface of a stream into which a stone had been cast, but, alas! without the after restoration of the latter.”

Dr. Cromwell,[36] citing the above instance of poetic inspiration during sleep, states that, having like Coleridge taken an anodyne during a painful illness, he composed the following lines of poetry, which he wrote down within half an hour after awaking. These lines, though displaying considerable imagination, are not remarkable for any other quality.

“Lines composed in sleep on the night of January 9th, 1857.

“Scene.—Windsor Forest.

“At a vista’s end stood the queen one day
Relieved by a sky of the softest hue;
It happen’d that a wood-mist risen new,
Had made that white which should have been blue.
A sunbeam sought on her form to play;
It found a nook in the bowery nave,
Through which with its golden stem to lave
And kiss the leaves of the stately trees
That fluttered and rustled beneath the breeze;
But it touched not her, to whom ’twas given
To walk in a white light pure as heaven.”

In the last two of these instances it is impossible to say whether the individuals were really asleep or not, as the opium or other narcotic taken is a very disturbing factor in both conditions, and doubtless was the exciting cause of the activity in the imagination. No more graphic account of the effects of opium in arousing the imagination to its highest pitch has been written than that given by De Quincey.[37] He says:

“At night when I lay awake in bed, vast processions passed along in mournful pomp; friezes of never-ending stories, that to my feelings were as sad and solemn as if they were stories drawn from times before Œdipus or Priam, before Tyre, before Memphis. And at the same time a corresponding change took place in my dreams; a theater seemed suddenly opened and lighted up within my brain, which presented nightly spectacles of more than earthly splendor.” And then, after referring to the various scenes of architectural magnificence, and of beautiful women which his imagination conceived, and which forcibly recalls to our minds the poetical effusions of Coleridge and Cromwell, he gives the details of another dream, in which he heard music. “A music of preparation, of awakening suspense; a music like the opening of the Coronation Anthem, and which like that gave the feeling of a vast march, of infinite cavalcades filing off, and the tread of innumerable armies.”

In reference to this subject, Dr. Forbes Winslow[38] relates the following interesting case:

“A feeble, sensitive lady, suffering from a uterine affection, writes to us as follows concerning the influence of three or four sixteenth-of-a-grain doses of hydrochlorate of morphia: ‘After taking a few doses of morphia, I felt a sensation of extreme quiet and wish for repose, and on closing my eyes, visions, if I may so call them, were constantly before me, and as constantly changing in their aspect: scenes from foreign lands; lovely landscapes, with tall, magnificent trees covered with drooping foliage, which was blown gently against me as I walked along. Then in an instant I was in a besieged city filled with armed men. I was carrying an infant, which was snatched from me by a soldier and killed upon the spot. A Turk was standing by with a scimitar in his hand, which I seized, and attacking the man who had killed the child, I fought most furiously with him and killed him. Then I was surrounded, made prisoner, carried before a judge and accused of the deed; but I pleaded my own cause with such a burst of eloquence (which, by-the-by, I am quite incapable of in my right mind) that judge, jury, and hearers acquitted me at once. Again, I was in an Eastern city visiting an Oriental lady, who entertained me most charmingly. We sat together on rich ottomans, and were regaled with supper and confectionery. Then came soft sounds of music at a distance, while fountains were playing and birds singing, and dancing girls danced before us, every movement being accompanied with the tinkling of silver bells attached to their feet. But all this suddenly changed, and I was entertaining the Oriental lady in my own house, and in order to please her delicate taste, I had everything prepared as nearly as possible after the fashion with which she had so enchanted me. She, however, to my no small surprise, asked for wine, and took not one, two, or three glasses, but drank freely, until at last I became terrified that she would have to be carried away intoxicated. While considering what course I had better adopt, several English officers came in, and she at once asked them to drink with her, which so shocked my sense of propriety that the scene changed and I was in darkness.

“‘Then I felt that I was formed of granite, and immovable. Suddenly a change came again over me, and I found that I consisted of delicate and fragile basket-work. Then I became a danseuse, delighting an audience and myself by movements which seemed barely to touch the earth. Presently beautiful sights came before me, treasures from the depth of the sea, gems of the brightest hues, gorgeous shells, coral of the richest colors, sparkling with drops of water, and hung with lovely seaweed. My eager glances could not take in half the beautiful objects that passed before me during the incessant changes the visions underwent. Now I was gazing upon antique brooches and rings from buried cities; now upon a series of Egyptian vases; now upon sculptured wood-work blackened by time; and lastly I was buried amid forests of tall trees, such as I had read of but never seen.

“‘The sights that pleased me most I had power to a certain extent to prolong, and those that displeased me I could occasionally set aside, and I awoke myself to full consciousness once or twice while under the influence of the morphia by an angry exclamation that I would not have it. I did not once lose my personal identity.’

“The lady almost invariably suffers more or less from hallucinations of the foregoing character, if it becomes necessary to administer to her an opiate: and on analyzing her visions, she can generally refer the principal portions of them, notwithstanding their confusion and distortion, to works that she has recently read.”

Opium, in certain doses, increases the amount of blood in the brain, and this induces a condition very different from that of sleep. In this fact we have an explanation of the activity of the imagination as one of its prominent effects. That Coleridge should have composed the Kubla Khan under its influence is in nowise remarkable. It is probable, however, that the full influence of his mind was exerted upon it after he awoke to consciousness, and that the wild fancies excited by the opiate, and based upon what he had been previously reading, formed the substratum of his conceptions. In any event, the ideas contained in this fragment are no more fanciful than those which occurred to De Quincey and the lady whose case has just been recorded, nor are they more impressively related.

The imagination may therefore be active during sleep, but we have no authentic instance on record that it has, unaided by causes which exercise a powerful influence over the intracranial circulation, led to the production of any ideas which could not be excelled by the individual when awake. Perhaps the most striking case in opposition to this opinion is one detailed by Abercrombie,[39] who says:

“The following anecdote has been preserved in a family of rank in Scotland, the descendants of a distinguished lawyer of the last age. This eminent person had been consulted respecting a case of great importance and much difficulty, and he had been studying it with intense anxiety and attention. After several days had been occupied in this manner, he was observed by his wife to rise from his bed in the night and go to a writing-desk which stood in the bed-room. He then sat down and wrote a long letter, which he put carefully by in the desk and returned to bed. The following morning he told his wife that he had had a most interesting dream; that he had dreamt of delivering a clear and luminous opinion respecting a case which had exceedingly perplexed him, and that he would give anything to recover the train of thought which had passed before him in his dream. She then directed him to the writing-desk, where he found the opinion clearly and fully written out, and which was afterwards found to be perfectly correct.”

It is probable that this gentleman was actually awake when he arose from the bed and wrote the paper referred to, and that in the morning he mistook the circumstance for a dream. It is not at all uncommon for such errors to be committed, especially under the condition of mental anxiety and fatigue. A gentleman informed me only a short time since that going to bed after a very exciting day he thought the next morning that he had dreamed of a fire occurring in the vicinity of his house. To his surprise his wife informed him that the supposed dream was a reality, and that he had got up to the window, looked at the fire, conversed with her concerning it, and that he was at the time fully awake.

Brierre de Boismont[40] relates the following instance, which is to the same effect:

“In a convent in Auvergne, an apothecary was sleeping with several persons; being attacked with nightmare, he charged his companions with throwing themselves on him and attempting to strangle him. They all denied the assertion, telling him that he had passed the night without sleeping, and in a state of high excitement. In order to convince him of this fact, they prevailed on him to sleep alone in a room carefully closed, having previously given him a good supper, and even made him partake of food of a flatulent nature. The paroxysm returned; but, on this occasion, he swore that it was the work of a demon, whose face and figure he perfectly described.”

That the imagination may in its flights during sleep strike upon fancies which are subsequently developed by the reason into lucid and valuable ideas, is very probable. It would be strange if from among the innumerable absurdities and extravagancies to which it attains something fit to be appropriated by the mind should not occasionally be evolved, and thus there are many instances mentioned of the starting-point of important mental operations having been taken during sleep. Some of these may be based upon fact, but the majority are probably of the class of those just specified, or occurred at an age of the world when a belief in the supernatural exercised a greater power over men’s minds than it does at the present day. Among the most striking of them are the following:

Galen declares that he owed a great part of his knowledge to the revelations made to him in dreams. Whether this was really the case or not we can in a measure determine by recalling the fact that he was a believer in the prophetic nature of dreams, and states that a man having dreamt that one of his legs was turned into stone, soon afterward became paralytic in this limb, although there was no evidence of approaching disease. Galen also conducted his practice by dreams, for an athlete, having dreamt that he saw red spots, and that the blood was flowing out of his body, was supposed by Galen to require blood-letting, which operation was accordingly performed.

It has been said[41] that the idea of the Divina Commedia occurred to Dante during sleep. There is nothing at all improbable in this supposition, though I have been unable to trace it to any definite source.

Cabanis[42] states that Condillac assured him that often during the course of his studies he had to leave them unfinished in order to sleep, and that on awaking he had more than once found the work upon which he was engaged brought to a conclusion in his brain.

These were clearly instances of “unconscious cerebration” of that power which the brain possesses to work out matters which have engaged its attention, without the consciousness of the individual being aroused to a knowledge of the labor being performed. It is not unlikely that this kind of mental activity goes on to some extent during sleep, but as it is of such a character that the mind does not take cognizance of its operations, I do not see how the exact period of its performance can be ascertained.

Jerome Cardan believed that he composed books while asleep, and his case is often adduced as an example of the height to which the imagination can attain during sleep. But this great man was superstitious to an extreme degree; he believed that he had a familiar spirit, from whom he received intelligence, warnings, and ideas, and asserted that when awake he frequently saw long processions of men, women, animals, trees, castles, instruments of various kinds and many figures, different from anything in this world. His evidence relative to his compositions and mathematical labors when asleep is not therefore of a trustworthy character.

As regards the memory in sleep, it is undoubtedly exercised to a considerable extent. In fact, whatever degree of activity the mind may then exhibit is based upon events the recollection of which has been retained. But there is more or less error mingled with a small amount of truth. The unbridled imagination of the sleeper so distorts the simplest circumstances as to render their recognition a matter of no small difficulty, and thus it scarcely if ever happens that events are reproduced during sleep exactly as they occurred or as they would be recalled by the mind of the individual when awake. Frequently, also, recent events which have made a strong impression on our minds are forgotten, as when we dream of seeing and conversing with persons not long dead.

And yet it has sometimes happened that incidents or knowledge which had long been overlooked or forgotten, or which could not be remembered by any effort during wakefulness have been strongly depicted during sleep. Thus Lord Monboddo[43] states that the Countess de Laval, a woman of perfect veracity and good sense, when ill, spoke during sleep in a language which none of her attendants understood, and which even she was disposed to regard as gibberish. A nurse detected the dialect of Brittany; her mistress had spent her childhood in that province, but had lost all recollection of the Breton tongue, and could not understand a word of what she said in her dreams. Her utterances applied, however, exclusively to the experience of childhood, and were infantile in structure.

Abercrombie[44] relates the case of a gentleman who was very fond of the Greek language, and who, in his youth, had made considerable progress in it. Subsequently being engaged in other pursuits, he so entirely forgot it that he could not even read the words; often, however, in his dreams he read Greek works, which he had been accustomed to use at college, and had a most vivid impression of fully understanding them.

Many other instances of the action of memory during sleep might be brought forward, but the subject will be more appropriately considered in the chapter on dreams.

The judgment is frequently exercised when we are asleep, but almost invariably in a perverted manner. In fact we scarcely ever estimate the events or circumstances which appear to transpire in our dreams at their real value, and very rarely from correct conceptions of right and wrong. High-minded and honorable men do not scruple during sleep to sanction the most atrocious acts, or to regard with complaisance ideas which, in their waking moments, would fill them with horror. Delicate and refined women will coolly enter upon a career of crime, and the minds of hardened villains are filled with the most elevated and noble sentiments. The deeds which we imagine we perform in our sleep are generally inadequate to or in excess of what the apparent occasion requires, and we lose so entirely the ideas of probability and possibility, that no preposterous vision appears otherwise than as perfectly natural and correct. Thus, a physician dreamed that he had been transformed into a monolith which stood grandly and alone in the vast desert of the Sahara, and had so stood for ages, while generation after generation wasted and melted away around him. Although unconscious of having organs of sense, this column of granite saw the mountains growing bald with age, the forests drooping with decay, and the moss and ivy creeping around its crumbling base.[45]

But, although in this instance there was some conception of time, as shown in the association of the evidences of decay with the lapse of years, there is in general no correct idea on this subject. Without going into details which more appropriately belong to another division of this treatise, I quote the following remarkable example from the essay last cited. It appeared originally in a biographical sketch of Lavalette, published in the Revue de Paris, and is related by Lavalette as occurring to him while in prison:

“One night, while I was asleep, the clock of the Palais de Justice struck twelve and awoke me. I heard the gate open to relieve the sentry, but I fell asleep again immediately. In this sleep I dreamt that I was standing in the Rue St. Honore. A melancholy darkness spread around me; all was still; nevertheless, a slow and uncertain sound soon arose. All of a sudden, I perceived at the bottom of the street and advancing toward me, a troop of cavalry,—the men and horses, however, all flayed. The men held torches in their hands, the red flames of which illuminated faces without skin, and bloody muscles. Their hollow eyes rolled fearfully in their sockets, their mouths opened from ear to ear, and helmets of hanging flesh covered their hideous heads. The horses dragged along their own skins in the kennels which overflowed with blood on all sides. Pale and disheveled women appeared and disappeared at the windows in dismal silence; low inarticulate groans filled the air, and I remained in the street alone petrified with horror, and deprived of strength sufficient to seek my safety in flight. This horrible troop continued passing along rapidly in a gallop, and casting frightful looks upon me. Their march continued, I thought, for five hours, and they were followed by an immense number of artillery wagons full of bleeding corpses, whose limbs still quivered; a disgusting smell of blood and bitumen almost choked me. At length the iron gates of the prison, shutting with great force, awoke me again. I made my repeater strike; it was no more than midnight, so that the horrible phantasmagoria had lasted no more than two or three minutes—that is to say, the time necessary for relieving the sentry and shutting the gate. The cold was severe and the watchword short. The next day the turnkey confirmed my calculations. I, nevertheless, do not remember one single event in my life the duration of which I have been able more exactly to calculate, of which the details are deeper engraven on my memory, and of which I preserve a more perfect consciousness.”

No instance can more strikingly exemplify aberration of the faculty of judgment than the above. There was no astonishment felt with the horror experienced, but all the impossible events which appeared to be transpiring were accepted as facts, which might have taken place in the regular order of nature.

An important question connected with the exercise of judgment is: does the dreamer know that he is dreaming? Some authors assert that this knowledge is possible, others that it is not. The following account is interesting, and I therefore transcribe it, especially as it has not to my knowledge been heretofore published in this country.

In a letter to the Rev. William Gregory, Dr. Thomas Reid[46] says:

“About the age of fourteen, I was almost every night unhappy in my sleep from frightful dreams. Sometimes hanging over a frightful precipice and just ready to drop down; sometimes pursued for my life and stopped by a wall or by a sudden loss of all strength; sometimes ready to be devoured by a wild beast. How long I was plagued by such dreams I do not now recollect. I believe it was for a year or two at least; and I think they had quite left me before I was fifteen. In those days I was much given to what Mr. Addison in one of his Spectators calls castle-building, and, in my evening solitary walk, which was generally all the exercise I took, my thoughts would hurry me into some active scene, where I generally acquitted myself much to my own satisfaction, and in these scenes of imagination I performed many a gallant exploit. At the same time, in my dreams, I found myself the most arrant coward that ever was. Not only my courage, but my strength failed me in every danger, and I often rose from my bed in the morning in such a panic that it took some time to get the better of it. I wished very much to get free of these uneasy dreams, which not only made me unhappy in sleep, but often left a disagreeable impression in my mind for some part of the following day. I thought it was worth trying whether it was possible to recollect that it was all a dream, and that I was in no real danger. I often went to sleep with my mind as strongly impressed as I could with this thought that I never in my lifetime was in any real danger, and that every fright I had was a dream. After many fruitless endeavors to recollect this when the danger appeared, I effected it at last, and have often, when I was sliding over a precipice into the abyss, recollected that it was all a dream, and boldly jumped down. The effect of this commonly was, that I immediately awoke. But I awoke calm and intrepid, which I thought a great acquisition. After this my dreams were never very uneasy, and, in a short time, I dreamed not at all.”

Beattie[47] states that he once dreamed that he was walking on the parapet of a high bridge. How he came there he did not know, but recollecting that he was not given to such pranks, he began to think it might all be a dream, and, finding his situation unpleasant, and being desirous to get out of it, threw himself headlong from the height, in the belief that the shock of the fall would restore his senses. The event turned out as he anticipated.

Aristotle also asserts that when dreaming of danger, he used to recollect that he was dreaming, and that he ought not to be frightened.

A still more remarkable narration is that of Gassendi,[48] which he thus relates as occurring to himself:

“A good friend of mine, Louis Charambon, judge of the criminal court at Digne, had died of the plague. One night, as I slept, I seemed to see him; I stretched out my arms toward him, and said, ‘Hail thou who returnest from the place of the dead!’ Then I stopped, reflecting in my dream as follows: ‘One cannot return from the other world; I am doubtless dreaming; but if I dream, where am I? Not at Paris, for I came last to Digne. I am then at Digne, in my house, in my bedroom, in my bed.’ And then, as I was looking for myself in the bed, some noise, I know not what, awoke me.”

In all these and like instances, it is very probable the individuals were much more awake than asleep, for certainly the power to judge correctly is not exercised in dreams, involving even the most incongruous impossibilities. As Dendy[49] says, “if we know that we are dreaming, the faculty of judgment cannot be inert, and the dream would be known to be a fallacy.” There would therefore be no occasion for any such management of it as that made use of by Reid and Beattie, or for the recollection of Aristotle. The dream and the correction of it by the judgment would go together and there would be no self-deception at all—not even for an instant. Dreams would accordingly be impossible. The essential feature of mental activity during sleep, absolute freedom of the imagination, would not exist.

Relative to Gassendi’s case, it is impossible to believe that he was fully asleep, and the fact that he was awakened by some noise, the nature of which was unrecognized, and which was therefore probably slight, tends to support this view. Moreover, although he was, as he thought, enabled to detect the fallacy of his dream in one respect, his judgment was altogether at fault in others. Thus he had great difficulty in making out where he was, and actually so far lost all idea of his identity with the person dreaming as to look for himself in his own bed! Certainly an individual whose judgment was thus much deranged would scarcely be able to reason correctly as to the fact of his dreaming or not, or to question the possibility of the dead returning to this world.

My opinion therefore is, that during sleep the power of bringing the judgment into action is suspended. We do not actually lose the power of arriving at a decision, but we cannot exert the faculty of judgment in accordance with the principles of truth and of correct reasoning. An opinion may therefore be formed during sleep, but it is more likely to be wrong than right, and no effort that we can make will enable us to distinguish the false from the true, or to discriminate between the possible and the impossible.

That faculty of the mind—the judgment—which when we are awake is pre-eminently our guide, can no longer direct us aright. The stores of experience go for naught, and the mind accepts as truth whatever preposterous thought the imagination presents to it. We are not entirely rendered incapable of judging, as some authors assert, but the power to perceive the logical force of circumstances, to take them at their true value and to eliminate error from our mental processes, is altogether arrested, and we arrive at absurd conclusions from impossible premises.

But there is no doubt that at times the faculty of judgment is suspended as regards some parts of our mental operations during sleep, and this, to such an extent, that we are like Gassendi in the case quoted, not capable of recognizing our own individuality. Thus it is related of Dr. Johnson, that he had once in a dream a contest of wit with some other person, and that he was very much mortified by imagining that his opponent had the better of him. “Now,” said he, “one may mark here the effect of sleep in weakening the power of reflection; for had not my judgment failed me, I should have seen that the wit of this supposed antagonist, by whose superiority I felt myself depressed, was as much furnished by me as that which I thought I had been uttering in my own character.”

Van Goens dreamt that he could not answer questions to which his neighbor gave correct responses.

An interesting case, in which the judgment was still more at fault, has recently come to my knowledge.

Mrs. C. dreamed that she was Savonarola, and that she was preaching to a vast assembly in Florence. Among the audience was a lady whom she at once recognized to be her own self. As Savonarola, she was delighted at this discovery, for she reflected that she was well acquainted with all Mrs. C.’s peculiarities and faults of character, and would, therefore, be enabled to give special emphasis to them in the sermon. She did this so very effectively that Mrs. C. burst into a torrent of tears, and, with the emotion thus excited, the lady awoke. It was some time before she was able to disentangle her mixed up individualities. When she became fully awake she perceived that the arguments she had employed to bring about the conversion of herself were puerile in the extreme, and were directed against characteristics which formed no part of her mental organization, and against offenses which she had not committed.

Macario[50] makes the following apposite remarks on the point under consideration. Referring to the preposterous nature of many dreams, he says:

“It is astonishing that all these fantastical and impossible visions seem to us quite natural, and excite no astonishment. This is because the judgment and reflection having abdicated, no longer control the imagination nor co-ordinate the thoughts which rush tumultuously through the brain of the sleeper, combined only by the power of association.

“When I say that the judgment and reflection abdicate, it should not be inferred that they are abolished and no longer exist, for the imagination could not, unaided by the reason, construct the whimsical and capricious images of dreams.”

Relative to the power to work out, during sleep, problems involving long and intricate mental processes, I have already expressed my opinion adversely. In this view, I am not alone. Rosenkranz,[51] whose contributions to psychological science cannot be overestimated, and whose clear and powerful understanding has rarely been excelled, has pointed out how such operations of the understanding are impossible; for, as he remarks, intellectual problems cannot be solved during sleep, for such a thing as intense thought, accompanied by images, is unknown, whilst dreams consist of a series of images connected by loose and imperfect reasoning. Feuchtersleben,[52] referring with approval to this opinion of Rosenkranz, says that he recollects perfectly having dreamt of such problems, and being happy in their solution, endeavored to retain them in his memory; he succeeded, but discovered, on awaking, that they were quite unmeaning, and could only have imposed upon a sleeping imagination.

Müller[53] says:

“Sometimes we reason more or less correctly in dreams. We reflect on problems and rejoice in their solution. But on awaking from such dreams, the seeming reasoning is frequently found to have been no reasoning at all, and the solution of the problem over which we had rejoiced, to be mere nonsense. Sometimes we dream that another person proposes an enigma; that we cannot solve it and that others are equally incapable of doing so; but that the person who proposed it, himself gives the explanation. We are astonished at the solution we had so long labored in vain to find. If we do not immediately awaken and afterwards reflect on this proposition of an enigma in our dream, and on its apparent solution, we think it wonderful; but if we awake immediately after the dream, and are able to compare the answer with the question, we find that it was mere nonsense.”

And in regard to the knowledge that we are dreaming, the same author[54] observes that:

“The indistinctness of the conception in dreams is generally so great that we are not aware that we dream. The phantasms which are perceived really exist in our organs of sense. They afford, therefore, in themselves as strong proof of the actual existence of the objects they represent, as our own perceptions of real external objects in the waking state; for we know the latter only by the affections of our senses which they produce. When, therefore, the mind has lost the faculty of analyzing the impressions on our senses, there is no reason why the things which they seem to represent should be supposed unreal. Even in the waking state phantasms are regarded as real objects when they occur to persons of feeble intellect. On the other hand, when the dreaming approaches more nearly to the waking state, we sometimes are conscious that we merely dream, and still allow the dream to proceed, while we retain this consciousness of its true nature.”

Sir Benjamin Brodie,[55] in discussing the subject of wonderful discoveries made in dreams, and abstruse problems worked out, remarks that it would indeed be strange if among the vast number of combinations which constitute our dreams, there were not every now and then some having the semblance of reality; and further, that in many of the stories of great discoveries made in dreams, there is much of either mistake or exaggeration, and that if they could have been written down at the time, they would have been found to be worth little or nothing.

Another faculty exercised during sleep has been ascribed to the judgment. It is well known that many persons having made up their minds to awake at a certain hour invariably do so. I possess this power in a high degree, and scarcely ever vary a minute from the fixed time. Just as I go to bed I look at my watch and impress upon my mind the figures on the dial which represent the hour and minute at which I wish to awake. I give myself no further anxiety on the subject, and never dream of it, but I always wake at the desired moment.

Now I cannot conceive what connection the judgment has with this power. In the case of alarm clocks set to go off at a certain time, the judgment, as Jouffroy[56] asserts, may take cognizance of the impression made upon the ear, and establish the relation between it and the wish to awake at a certain time. But in cases where the awaking is the result of an idea conceived before going to sleep, and which is not subsequently recalled, the judgment cannot act, for this faculty is only exercised upon ideas which are submitted to it. The brain is, as it were, wound up like the alarm clock and set to a certain hour. When that hour arrives, an explosion of nervous force takes place, and the individual awakes.

Fosgate[57] asserts that the power of judging during sleep is probably as good as when we are awake, for decisions are made only on the premises presented in either case, and if those in the former condition are absurd or unreasonable, the conclusion will likewise be faulty. But this is not very accurate reasoning; for it is as much the province of the judgment to determine the validity of the premises as it is to draw a conclusion from them, and if it cannot recognize the falsity or truth of propositions the irrational character of which would be readily perceived during wakefulness, there is not much to be said in favor of its power.

In fact, however, the conclusions formed in dreams are often without any logical relation with the premises. Thus, when an individual dreams, as in the instance previously quoted, that he is a column of stone, it is contrary to all experience to deduce therefrom the conclusion that he can see rocks crumbling around him, and can reflect upon the mutability of all things. The premise of his being a stone pillar being submitted to the judgment, the proper conclusion would be that he is composed of inorganic material, is devoid of life, and consequently not possessed of either sensation or understanding.

Why the judgment is not properly exercised during sleep we do not know. Dr. Philip[58] believes that in this condition ideas flow so rapidly that they are not submitted to the full power of the judgment, and that hence the absurdity which characterizes them is not perceived. But this explanation is by no means satisfactory; for a merely swift succession of ideas is no very serious bar to correct judgment, and when the thoughts are as preposterous as those which so often occur in dreams, they present no obstacle at all to a proper estimation of them by the healthy mind. The cause probably resides in some alteration in the circulation of the blood in that part of the brain which presides over the judgment, whereby its power is suspended and the imagination left free to fill the mind with its incongruous and fantastic images.

As regards the will, we find very opposite opinions entertained relative to its activity; but no one, so far as I am aware, appears to have had correct views upon the subject. Without going into a full discussion of the views enunciated, it will be sufficient to refer to the ideas on the point in question which have been expressed by some of the most eminent philosophers and physiologists.

In the course of his remarks on sleep, Darwin[59] repeatedly alleges that during this condition the action of the will is entirely suspended; but he falls into the singular error of confounding volition with the power of motion. Thus he says:

“When by one continued posture in sleep some uneasy sensations are produced, we either gradually awake by the exertion of volition, or the muscles connected by habit with such sensations alter the position of the body; but where the sleep is uncommonly profound, and these uneasy sensations great, the disease called the incubus or nightmare is produced. Here the desire of moving the body is painfully exerted; but the power of moving it, or volition, is incapable of action till we are awake.”

In consequence of this misapprehension of the nature of the will, it is not easy to arrive at Darwin’s ideas on the subject; and the attempt is rendered still more difficult from the fact that though he repeatedly states that volition is entirely suspended during sleep, he yet in the first part of the foregoing quotation makes an individual awake by the gradual exercise of the power of the will; and then in the last part of the same paragraph asserts that volition is incapable of action till sleep is over.

Mr. Dugald Stewart[60] contends that during sleep the power of volition is not suspended, but that those operations of the mind and body which depend on volition cease to be exercised. In his opinion the will loses its influence over all our powers both of mind and body in consequence of some physical alteration in the system which we shall never probably be able to explain. To show in full the views of so distinguished a philosopher as Mr. Stewart, I quote the following extracts from his remarks on the subject:

“In order to illustrate this conclusion [the one above stated] a little further, it may be proper to remark that if the suspension of our voluntary operations in sleep be admitted as a fact, there are only two suppositions which can be formed regarding its cause. The one is that the power of volition is suspended; the other that the will loses its influence over those faculties of the mind and those members of the body which during our waking hours are subjected to its authority. If it can be shown then that the former supposition is not agreeable to fact, the truth of the latter seems to follow as a necessary consequence.

“1. That the power of volition is not suspended during sleep, appears from the efforts which we are conscious of making while in that situation. We dream, for instance, that we are in danger, and we attempt to call out for assistance. The attempt induced is in general unsuccessful, and the sounds that we emit are feeble and indistinct; but this only confirms, or rather is a necessary consequence of, the supposition that in sleep the connection between the will and our voluntary operations is disturbed or interrupted. The continuance of the power of volition is demonstrated by the effort, however ineffectual.

“In like manner, in the course of an alarming dream we are sometimes conscious of making an exertion to save ourselves by flight from an apprehended danger; but in spite of all our efforts we continue in bed. In such cases we commonly dream that we are attempting to escape and are prevented by some external obstacle; but the fact seems to be that the body is at that time not subject to the will. During the disturbed rest which we sometimes have when the body is indisposed, the mind appears to retain some power over it; but as even in these cases the motions which are made consist rather of a general agitation of the whole system than of the regular exertion of a particular member of it with a view to produce a certain effect, it is reasonable to conclude that in perfectly sound sleep the mind, although it retains the power of volition, retains no influence whatever over the bodily organs.

“In that particular condition of the system which is known by the name of incubus, we are conscious of a total want of power over the body; and I believe the common opinion is that it is this want of power which distinguishes the incubus from all the other modifications of sleep. But the more probable supposition seems to be that every species of sleep is accompanied with a suspension of the faculty of voluntary motion; and that the incubus has nothing peculiar in it but this—that the uneasy sensations which are produced by the accidental posture of the body, and which we find it impossible to remove by our own efforts, render us distinctly conscious of our incapacity to move. One thing is certain, that the instant of our awaking and of our recovering the command of our bodily organs is one and the same.

“2. The same conclusion is confirmed by a different view of the subject. It is probable, as was already observed, that when we are anxious to procure sleep the state into which we naturally bring the mind approaches to its state after sleep commences. Now it is manifest that the means which nature directs us to employ on such occasions is not to suspend the powers of volition, but to suspend the exertion of those powers whose exercise depends on volition. If it were necessary that volition should be suspended before we fall asleep, it would be impossible for us by our own efforts to hasten the moment of rest. The very supposition of such efforts is absurd, for it implies a continued will to suspend the acts of the will.

“According to the foregoing doctrine with respect to the state of the mind in sleep, the effort which is produced on our mental operations is strikingly analogous to that which is produced on our bodily powers. From the observations which have been already made, it is manifest that in sleep the body is in a very inconsiderable degree, if at all, subject to our command. The vital and involuntary motions, however, suffer no interruption, but go on as when we are awake, in consequence of the operation of some cause unknown to us. In like manner it would appear that those operations of the mind which depend on our volition are suspended, while certain other operations are at least occasionally carried on. This analogy naturally suggests the idea that all our mental operations which are independent of our will may continue during sleep; and that the phenomena of dreaming may, perhaps, be produced by these, diversified in their apparent effects in consequence of the suspension of our voluntary powers.”

A very little reflection will suffice to convince the reader that Mr. Stewart has altogether mistaken the nature of sleep. There is no evidence to support his view that the body is not subject to the action of the will during sleep. No change whatever is induced by this condition in the nerves or muscles of the organism. The first are just as capable as ever of conducting the nervous fluid, and the muscles do not lose any of their contractile power. The reason why voluntary movements are not performed in sleep is simply because the will does not act; and Mr. Stewart is again wrong in asserting that volition is not then suspended. We do not will any actions when we are asleep. We imagine we do, and that is all. The difficulties which encompass us in sleep are, it must be recollected, purely imaginary, and the efforts we make to escape from them are likewise the products of our fancy. Herein lies the main error which Mr. Stewart has committed. He appears to accept the dream for a reality, and to regard the seeming volitions which occur in it as actual facts; whereas they are all entirely fictitious.

An example will serve to make this point still clearer.

Not long since I dreamed that I stood upon a very high perpendicular table-land, at the foot of which flowed a river. I thought I experienced an irresistible desire to approach the brink and to look down. Had I been awake, such a wish would have been the very last to enter my mind, for I have an instinctive dread of standing on a height. I dreamed that I threw myself on my face and crawled to the edge of the cliff. I looked down at the stream, which scarcely appeared to be as wide as my hand, so great was the altitude upon which I was placed. As I looked I felt an overpowering impulse to crawl still farther and to throw myself into the water below. I imagined that I endeavored with all my will to resist this force, which appeared to be acting by means altogether external to my organism. My efforts, however, were all in vain. I could not control my movements, and gradually I was urged farther and farther over the brink, till at last I went down into the abyss below. As I struck the water I awoke with a start. During my imaginary struggle I thought I experienced all the emotions which such an event if real would have excited, and I was painfully conscious of my utter inability to escape from the peril of my situation. Here were circumstances such as, according to Mr. Stewart, demonstrate the activity of volition, but at the same time show its inability to act upon the body. But clearly they show no such thing, for the imaginary volition was to refrain from crawling over a precipice which did not exist, and over which, therefore, I was not hanging. Such an act of the will if real, could not in the very nature of the real conditions of the situation have been carried out—the volition was just as imaginary as all the other circumstances of the dream.

Again, it is not always the case that the imaginary acts of the will are not executed during sleep; and hence it would follow from Mr. Stewart’s argument that the power of the will over the body is not then suspended. Assuming for the moment that the volitions of sleep are real, as Mr. Stewart supposes; if it can be shown that they are satisfactorily performed, it results from his line of reasoning that the will has power over the body during sleep. Every one who has ever dreamed has at times had his will carried out to his entire satisfaction. He has ridden horses when pursued, and has urged them forward with whip and spur so as to escape from his enemies. Or he has executed the most surprising feats both with his mind and body, and has performed voluntary deeds which have excited the admiration of all beholders. Such acts are of course entirely the product of the imagination, and all the volitions which accompany them have no firmer basis than the unbridled fancy; but, according to Mr. Stewart, they would be evidence of the power of the will over the body,—a power which in reality does not exist; not, however, as Mr. Stewart supposes from any impediments in the nerves or muscles, but because it is never exerted.

So far as relates to movements performed during sleep, such as turning in bed and assuming more comfortable positions, they have nothing whatever to do with the will. They are dependent upon the action of the spinal cord, an organ that is never at rest, and the functions of which were not known as well when Dr. Darwin and Mr. Stewart wrote as they are now. The same is true of more complex and longer-continued actions, such as those already mentioned of individuals riding on horseback, or even walking, during sleep.

Cabanis[61] contends that the will is not entirely suspended during sleep; but, as will be perceived from the following quotation, he bases his argument upon the fact that movements are produced which he attributes erroneously to the action of the will, but which, like those previously referred to, are accomplished by the agency of the spinal cord. He says, speaking of the instances of persons walking while asleep:

“These rare cases are not the only ones in which during sleep movements are produced by what remains of the will; for it is by virtue of certain direct sensations that a sleeping man moves his arm to brush away the flies that may be on his face, that he draws up the bedclothes so as to cover himself carefully; or, as we have already remarked, that he turns over and endeavors to find a more comfortable position. It is the will which during sleep maintains the contraction of the sphincter of the bladder, notwithstanding the effort of the urine to escape; it is the same power which directs the action of the arm in seeking for the vase de nuit, which knows where to find it, and enables the individual to use it for several minutes and to return it to its place without being awakened. Finally, it is not without reason that some physiologists have made the will concur in the contraction of several muscles, the movements of which are necessary to the maintenance of respiration during sleep.”

All these movements, and many others of a similar character, are entirely spinal, and are altogether independent of cerebral influence. Even when we are awake, we constantly execute muscular actions through the power of the spinal cord, when the mind is intently occupied with other things. Take for instance the example of a person playing on the piano, and at the same time carrying on a conversation. Here the brain is engaged in the one act and the spinal cord in the other. So long as the player is not expert in the fingering of the instrument, he cannot divert his attention from his performance; for the whole power of the mind is required for the proper appreciation and execution of the music. But after the spinal cord has become educated to the habit, and he has attained proficiency in the necessary manipulations, the mind is no longer required to control the actions and may be directed to other subjects. The arguments of Cabanis, therefore, in favor of the partial exercise of the will during sleep, are of no force.

But the power of the will over the muscles of the body is only one of the ways in which this faculty is shown. It regulates the thoughts and the manifestations of emotion when we are awake. How utterly incapable it is of any such action during sleep we all know. A gentleman, remarkable for the ability he possesses for controlling his feelings, tells me that when he is asleep he frequently weeps or laughs at imaginary events, which, if they really had occurred to him during wakefulness, would give rise to no such disturbance. He often desires to stop these emotional manifestations, but is entirely powerless to do so. Most individuals have had similar experiences.

The theory that the will is in action during sleep is, therefore, to my mind untenable. It has probably had its origin in the idea that confounds it with desire, from which it differs so markedly that it seems strange the distinction should ever fail of being made. Locke[62] points out very clearly the differences between the two faculties. In fact they may be exerted in directly opposite ways. Desire often precedes volition; but we all, at times, will acts which are contrary to our desire, and desire to perform others which we are unable to will.

Reid[63] writes with great perspicuity on this distinction between desire and will. He says:

“Desire and will agree in this, that both must have an object of which we must have some conception; and, therefore, both must be accompanied with some degree of understanding. But they differ in several things.

“The object of desire may be anything which appetite, passion, or affection leads us to pursue; it may be any event which we think good for us, or for those to whom we are well affected. I may desire meat or drink, or ease from pain. But to say that I will meat, or will drink, or will ease from pain, is not English. There is, therefore, a distinction in common language between desire and will. And the distinction is, that what we will must be an action and our own action; what we desire may not be our own action, it may be no action at all.

“A man desires that his children may be happy, and that they may behave well. Their being happy is no action at all; their behaving well is not his action but theirs.

“With regard to our own actions, we may desire what we do not will, and will what we do not desire; nay, what we have a great aversion to.

“A man athirst has a strong desire to drink; but for some particular reason he determines not to gratify his desire. A judge from a regard to justice and to the duty of his office dooms a criminal to die; while, from humanity or particular affection, he desires that he should live. A man for health may take a nauseous draught, for which he has no desire, but a great aversion. Desire, therefore, even when its object is some action of our own, is only an incitement to will; but it is not volition. The determination of the mind may be not to do what we desire to do. But as desire is often accompanied by will, we are apt to overlook the distinction between them.”

That desire is manifested during sleep there can be no doubt; and Mr. Stewart, although insisting as he does on the distinction between this faculty and volition, confounds them in his remarks already quoted. A person suffering from nightmare has a most intense desire to escape from his imaginary troubles. In my own dream, to which reference has been made, my desire to restrain myself from crawling over the precipice was exerted to the utmost; but the will could not be brought into action. Darwin,[64] when he says that in nightmare “the desire of moving the body is painfully exerted, but the power of moving it, or volition, is incapable of action till we awake,” makes the proper distinction between desire and will; but, as I have already shown, confounds the latter with another very different faculty.

From the foregoing observations it will be seen that during sleep the three great divisions of the mind are differently affected.

1. Feeling, embracing sensation and emotion, is suspended, so far as the first is concerned; but is in full action as regards the second. We do not see, hear, smell, taste or enjoy the sense of touch in sleep, although the brain may be aroused into activity and we may awake through the excitations conveyed to it by the special senses. The emotions have full play, unrestrained by the will and governed only by the imagination.

2. The Will or Volition is entirely suspended.

3. The Thought or Intellect is variously affected in its different powers. The imagination is active, and the memory may be exercised to a great extent; but the judgment, perception, conception, abstraction, and reason are weakened, and sometimes altogether lost.

CHAPTER V.

THE PHYSIOLOGY OF DREAMS.

The subject of the foregoing chapter is so intimately connected with the phenomena of dreaming, and I have expressed my views in regard to it at such length, that but few psychological points remain to be considered in the present discussion. What I have to say, therefore, in regard to the physiology of dreaming must be read in connection with the chapter on “The State of the Mind during Sleep,” in order that the whole matter may be fully understood.

It is contended by some writers that the mind is never at rest, and that even during the most profound sleep dreams take place, which are either forgotten immediately, or which make no impression on the memory. That this view is erroneous is, I think, very evident. If it were correct, the first object of sleep—rest for the brain—would not be attained. We all know how fatigued we are, and how indisposed to exertion the brain is, after a night of continued dreaming, and we can easily imagine what would be the consequences if such a condition were kept up night after night. To say that we really do dream not only every night, but every instant of the night, in fact always and continually when we sleep, but that we forget our dreams as soon as they are formed, remembering solely those which are most vivid, is making assertions which not only are without proof, but which are impossible of proof. For if, as Locke[65] remarks, the sleeping man on awaking has no recollection of his thoughts, it is very certain that no one else can recollect them for him.

The observations of Locke on this point are extremely appropriate, and, to my mind, very philosophical and logical. After insisting that, sleeping or waking, a man cannot think without being sensible of it, he says:[66]

“I grant that the soul of a waking man is never without thought, because it is the condition of being awake; but whether sleeping without dreaming be not an affection of the whole man, mind as well as body, may be worth a waking man’s consideration, it being hard to conceive that anything should think and not be conscious of it. If the soul doth think in a sleeping man without being conscious of it, I ask, whether during such thinking it has any pleasure or pain, or be capable of happiness or misery? I am sure the man is not, any more than the bed or earth he lies on, for to be happy or miserable without being conscious of it seems to me utterly inconsistent and impossible. Or if it be possible that the soul can, while the body is sleeping, have its thinkings, enjoyments, and concerns, its pleasure or pain, about which the man is not conscious of nor partakes in, it is certain that Socrates asleep and Socrates awake is not the same person; but his soul when he sleeps and Socrates the man, consisting of body and soul when he is waking, are two persons, since waking Socrates has no knowledge of or concernment for that happiness or misery of his soul which it enjoys alone by itself while he sleeps without perceiving anything of it, any more than he has for the happiness or misery of a man in the Indies whom he knows not; for if we take wholly away all consciousness of our actions and sensations, especially of pleasure and pain, and the concernment that accompanies it, it will be hard to know wherein to place personal identity.”

In a subsequent section of the same chapter, Locke asserts that most men pass a great part of their lives without dreaming, and that he once knew a scholar who had no bad memory, who told him he had never dreamed in his life till after the occurrence of a fever in the twenty-fifth or twenty-sixth year of his age.

Examples of persons who have not ordinarily dreamed are adduced by the ancient writers. Pliny[67] refers to men who never dreamed. Plutarch[68] alludes to the case of Cleon, who, in living to an advanced age, had yet never dreamed; and Suetonius[69] declares that before the murder of his mother he had never dreamed.

A lady who was under my care for a serious nervous affection declared to me that she never had had but one dream in her life, and that was after receiving a severe fall in which she struck her head.

And yet, notwithstanding the experience of every one that sleep often happens without the accompaniment of dreams, the great majority of writers hold the view that the brain is never at rest. Doubtless this opinion has its origin partly in the doctrine that the mind is a something altogether independent of and superior to the brain. They appear to be incapable of appreciating the fact that when the brain is in a state of complete repose there can be no mental manifestation, and that all intellectual phenomena are the results of cerebral activity. Another cause for their belief is the fact that they make no distinction between dreaming and thinking, whereas it is very evident that the two are not to be placed in the same category. Thinking is an action which requires cerebral effort, and which is undertaken with a determinate purpose. We will to think, and we think what we please; but it is very different with our dreams, which come and go without any power on our part to regulate or direct them. To think requires all the faculties of the mind; to dream necessitates only the memory and the imagination. In thinking, the brain is active in all its parts; in dreaming, it is nearly entirely quiescent.

Writers who contend for the doctrine of constant mental activity regard the brain as the organ or tool of the mind, a structure which the mind makes use of in order to manifest itself. Such a theory is certain to lead them into difficulties, and is contrary to all the teaching of physiology. The full discussion of this question would be out of place here; I will, therefore, only state that this work is written from the stand-point of regarding the mind as nothing more than the result of cerebral action. Just as a good liver secretes good bile, a good candle gives good light, and good coal a good fire, so does a good brain give a good mind. When the brain is quiescent there is no mind.

Lemoine[70] begins his chapter “On the State of the Mind during Sleep” with the assertion that “there is no sleep for the mind.” He is obliged, however, to admit that “when the organs of the body are benumbed by sleep, the mind appears to be in a particular state; it seems to be submitted to other laws than those which govern it during wakefulness; it seems to have lost for a time its most precious faculties.”

During sleep the mind is, as he supposes, in a particular state, for, as has been shown in the previous chapter, it has lost many of its chief parts. The laws which govern it are, however, the same which always regulate it. The body upon which their power is primarily exercised—the brain—is not in the same condition during sleep as during wakefulness, and hence the differences in the evidences of cerebral activity.

Sir William Hamilton[71] is generally considered to have determined affirmatively the question of the continuance of the action of the brain during sleep. He caused himself to be aroused from sleep at intervals through the night, and invariably found that he was disturbed from a dream, the particulars of which he could always distinctly recollect. But a full knowledge of the subject he was investigating would have sufficed to convince Sir William that the conclusion he drew from his experiments was altogether fallacious. It is well known that dreams are excited by strong impressions made upon the senses, or by irritations arising in the internal organs. Thus Baron Trenck relates that when confined in his dungeon he suffered the pangs of hunger almost continually, and that his dreams at night were always of delicate meats and sumptuous repasts, spread before him on luxuriously-furnished tables. The mere excitation of waking a sleeping person is generally sufficient to give rise to a dream. Maury, in his very interesting work, to which reference has already been made, and which will hereafter be more specifically considered, adduces many examples of dreams produced by sensorial impressions. I have myself performed many experiments with reference to this point, and have generally found ample confirmation of Maury’s investigations. It may therefore, I think, be assumed, without any violence to the actual facts of the cases, that the brain is not always in action, and that there are times when we sleep without dreaming.

In the previous chapter the idea is sought to be conveyed that we originate nothing in our dreams. We may conceive of things which never existed, or of which we have heard or read, but the images we make of them are either composed of elements familiar to us, or else are based upon ideal representations which we have formed in our waking moments. Thus, before the discovery of America no Europeans ever dreamed of American Indians, for the reason that nothing existed within their knowledge which could give any idea of the appearance of such human beings. It is possible that Columbus and his companions may have dreamed of the continent of which they were in search and of its natives, but the images formed of the latter must necessarily have resembled other beings they had seen, or which they had heard described. After the discovery, however, it was no unusual thing for the Spaniards and others to have correct images of Indians appear to them in their dreams.

Dreams, therefore, must have a foundation, and this is either impressions made upon the mind at some previous period, or produced during sleep by bodily sensations. These impressions, however they may be formed, are subjected to the unrestrained influence of the imagination.

At first sight it may seem that we often have dreams not excited by actual sensations, and which have no relation to any events of our lives, or any ideas which have passed through our minds, but thorough investigation will invariably reveal the existence of an association between the dream and some such ideas or events. For instance, a few nights ago I dreamed that a gentleman, a friend of mine, had invented what he called a “dog-cart ambulance,” a vehicle which he declared was the best ever made for the transportation of sick or wounded men. On awaking, all the particulars were fresh in my mind, but I could not for some time perceive why I had had such a dream. At last I recollected that the morning before a gentleman had given me a very full description of Prospect Park, in Brooklyn. The friend of whom I dreamed has charge of the construction of this Park. His presence was, therefore, fully explained, and as dog-carts are driven in parks, this link was also accounted for. The ambulance part was due to the fact that I had that same morning found the card of a gentleman upon my table who really had invented an ambulance. The imagination had, therefore, taken these data supplied by the memory, and had combined them into the incongruous web constituting my dream.

Dreams are also frequently built upon circumstances which have transpired many years previously, and which have long since apparently passed from our recollection. A very striking instance of this kind is related by Abercrombie,[72] on the authority of Sir Walter Scott.

“Mr. R. J. Rowland, a gentleman of landed property in the vale of Gala, was prosecuted for a very considerable sum, the accumulated arrears of teind (tithe), for which he was said to be indebted to a noble family the titulars (lay impropriators of the tithe). Mr. R. was strongly impressed with the belief that his father had, by a form of process peculiar to the law of Scotland, purchased these teinds from the titular, and, therefore, that the present prosecution was groundless. But after an industrious search among his father’s papers, an investigation of the public records, and a careful inquiry among all persons who had transacted law business for his father, no evidence could be discovered to support his defense. The period was now near at hand when he conceived the loss of his lawsuit to be inevitable, and he had formed his determination to ride to Edinburgh next day, and make the best bargain he could in the way of compromise. He went to bed with this resolution, and, with all the circumstances of the case floating upon his mind, had a dream to the following purpose. His father, who had been many years dead, appeared to him, he thought, and asked him why he was disturbed in his mind. In dreams men are not surprised at such apparitions. Mr. R. thought that he informed his father of the cause of his distress, adding that the payment of a considerable sum of money was the more unpleasant to him, because he had a stray consciousness that it was not due, though he was unable to recover any evidence in support of his belief. ‘You are right, my son,’ replied the paternal shade; ‘I did acquire right to these teinds, for payment of which you are now prosecuted. The papers relating to the transaction are in the hands of Mr. ——, a writer (or attorney), who is now retired from professional business, and resides at Inveresk, near Edinburgh. He was a person whom I employed on that occasion for a particular reason, but who never, on any other occasion, transacted business on my account. It is very possible,’ pursued the vision, ‘that Mr. —— may have forgotten a matter which is now of a very old date; but you may call it to his recollection by this token—that when I came to pay his account there was difficulty in getting change for a Portugal piece of gold, and that we were forced to drink out the balance at a tavern.’

“Mr. R. awaked in the morning with all the events of the vision impressed on his mind, and thought it worth while to ride across the country to Inveresk, instead of going straight to Edinburgh. When he came there he waited on the gentleman mentioned in the dream, a very old man; without saying anything of the vision, he inquired whether he remembered having conducted such a matter for his deceased father. The old gentleman could not at first bring the circumstance to his recollection, but, on mention of the Portugal piece of gold, the whole returned upon his memory; he made an immediate search for the papers and recovered them, so that Mr. R. carried to Edinburgh the documents necessary to gain the cause which he was on the verge of losing.”

A friend has related to me some circumstances in his own case similar to the above, and illustrating the same points. In the course of his practice as a lawyer, it became necessary for him to ascertain the exact age of a client, who was also his cousin. Their grandfather had been a rather eccentric personage, who had taken a great deal of notice of both his grandsons—his only direct descendants. He died when they were boys. My friend often told his cousin that if his grandfather were alive there would be no difficulty at getting at the desired information, and that he had a dim recollection of having seen a record kept by the old gentleman, and of there being some peculiarity about it which he could not recall. Several months elapsed, and he had given up the idea of attempting to discover the facts of which he had been in search, when, one night, he dreamed that his grandfather came to him and said: “You have been trying to find out when J—— was born; don’t you recollect that one afternoon when we were fishing I read you some lines from an Elzevir Horace, and showed you how I had made a family record out of the work by inserting a number of blank leaves at the end? Now, as you know, I devised my library to the Rev. —— ——. I was a d——d fool for giving him books which he will never read! Get the Horace, and you will discover the exact hour at which J—— was born.” In the morning all the particulars of this dream were fresh in my friend’s memory. The reverend gentleman lived in a neighboring city; my friend took the first train, found the copy of Horace, and at the end the pages constituting the family record, exactly as had been described to him in the dream. By no effort of his memory, however, could he recollect the incidents of the fishing excursion.

Dr. Macnish,[73] in stating his opinion that dreams are uniformly the resuscitation or re-embodiment of thoughts which have formerly, in some shape or other, occupied the mind, relates the following example from his own experience:

“I lately dreamed that I walked upon the banks of the great canal in the neighborhood of Glasgow. On the side opposite to that on which I was, and within a few feet of the water, stood the splendid portico of the Royal Exchange. A gentleman whom I knew was standing upon one of the steps, and we spoke to each other. I then lifted a large stone and poised it in my hand, when he said that he was certain I could not throw it to a certain spot, which he pointed out. I made the attempt, and fell short of the mark. At this moment a well-known friend came up, whom I knew to excel at putting the stone; but, strange to say, he had lost both his legs, and walked upon wooden substitutes. This struck me as exceedingly curious, for my impression was that he had only lost one leg, and had but a single wooden one. At my desire he took up the stone, and, without difficulty, threw it beyond the point indicated by the gentleman upon the opposite side of the canal. The absurdity of this dream is extremely glaring, and yet, on strictly analyzing it, I find it to be wholly composed of ideas which passed through my mind on the previous day, assuming a new and ridiculous arrangement. I can compare it to nothing but to cross reading in the newspapers, or to that well-known amusement which consists in putting a number of sentences, each written on a separate piece of paper, into a hat, shaking the whole, then taking them out, one by one, as they come, and seeing what kind of medley the heterogeneous compound will make when thus fortuitously put together. For instance, I had, on the above day, taken a walk to the canal along with a friend. On returning from it, I pointed out to him a spot where a new road was forming, and where, a few days before, one of the workmen had been overwhelmed by a quantity of rubbish falling upon him, which fairly chopped off one of his legs, and so much damaged the other that it was feared amputation would be necessary. Near this very spot there is a park, in which, about a month previously, I practiced throwing the stone. On passing the Exchange, on my way home, I expressed regret at the lowness of its situation, and remarked what a fine effect the portico would have were it placed upon more elevated ground. Such were the previous circumstances, and let us see how they bear upon the dream. In the first place, the canal appeared before me. 2. Its situation is an elevated one. 3. The portico of the Exchange occurring to my mind as being placed too low became associated with the elevation of the canal, and I placed it close by on a similar altitude. 4. The gentleman I had been walking with was the same whom in the dream I saw standing upon the steps of the portico. 5. Having related to him the story of the man who lost one limb and had a chance of losing another, this idea brings before me a friend with a pair of wooden legs, who, moreover, appears in connection with patting the stone, as I knew him to excel at that exercise. There is only one other element in the dream which the preceding events will not account for, and that is the surprise at the individual referred to having more than one wooden leg. But why should he have even one, seeing that in reality he is limbed like other people? This also I can account for. Two years ago he slightly injured his knee while leaping a ditch, and I remember jocularly advising him to get it cut off. I am particular in illustrating this point with regard to dreams, for I hold that if it were possible to analyze them all, they would invariably be found to stand in the same relation to the waking state as the above specimen. The more diversified and incongruous the character of a dream, and the more remote from the period of its occurrence the circumstances which suggested it, the more difficult does its analysis become; and, in point of fact, this process may be impossible, so totally are the elements of the dream often dissevered from their original sense, and so ludicrously huddled together.”

A dream which Professor Maas,[74] of Halle, relates as having occurred to himself, affords an excellent example of the dependence of dreams upon actual events, and shows how these latter are distorted and perverted by the imagination of the sleeper.

“I dreamed once,” he says, “that the Pope visited me. He commanded me to open my desk, and he carefully examined all the papers it contained. While he was thus employed, a very sparkling diamond fell out of his triple crown into my desk, of which, however, neither of us took any notice. As soon as the Pope had withdrawn I retired to bed, but was soon obliged to rise on account of a thick smoke, the cause of which I had yet to learn. Upon examination I discovered that the diamond had set fire to the papers in my desk, and burned them to ashes.”

In analyzing the circumstances which gave rise to this dream, Professor Maas relates the following events, which constituted its basis:

“On the preceding evening I was visited by a friend with whom I had a lively conversation upon Joseph II.’s suppression of monasteries and convents. With this idea, though I did not become conscious of it in the dream, was associated the visit which the Pope publicly paid the Emperor Joseph, at Vienna, in consequence of the measures taken against the clergy; and with this again was combined, however faintly, the representation of the visit which had been paid me by my friend. These two events were, by the subreasoning faculty, compounded into one, according to the established rule—that things which agree in their parts also correspond as to the whole; hence the Pope’s visit was changed into a visit paid to me. The subreasoning faculty, then, in order to account for this extraordinary visit, fixed upon that which was the most important object in my room—namely, the desk, or rather the papers which it contained. That a diamond fell out of the triple crown was a collateral association, which was owing merely to the representation of the desk. Some days before, when opening the desk, I had broken the crystal of my watch, which I held in my hand, and the fragments fell among the papers; hence no further attention was paid to the diamond being a representation of a collateral series of things. But afterwards the representation of the sparkling stone was again excited, and became the prevailing idea; hence it determined the succeeding association. On account of its similarity it excited the representation of fire, with which it was confounded; hence arose fire and smoke. But in the event the writings only were burned, not the desk itself, to which, being of comparatively little value, the attention was not directed.”

Feuchtersleben[75] takes the same view of dreaming as that enunciated in this chapter. Thus he says:

“Dreaming is nothing more than the occupation of the mind in sleep with the pictorial world of fancy. As the closed or quiescent senses afford it no materials, the mind, ever active, must make use of the store which memory retains; but as its motor influence is likewise organically impeded, it cannot independently dispose of this store. Thus arises a condition in which the mind looks, as it were, on the play of the images within itself, and manifests only a faint or partial reaction.”

Locke[76] contends that “the dreams of a sleeping man are all made up of the waking man’s ideas oddly put together.”

Observation and reflection show us that the mind originates nothing during sleep; it merely remembers—and often in the most chaotic manner—the thoughts, the fancies, the impressions which have been imagined or received by the individual when awake. Sometimes ideas are reproduced in dreams exactly as they have occurred to us in our waking moments, and this may take place night after night with scarcely the alteration of a single circumstance. A friend informs me that he is very subject to dreams of this character, and that on some occasions the repetition has taken place as many as a dozen times.

A very striking instance of this kind occurred to me a few years since, and made a deep impression on my mind. I had just read Schiller’s ode to Laura, as translated by Sir E. Bulwer Lytton, beginning,