SECTION III. THE Connections of sleep with insanity are so intimate and numerous that the consideration of this important function in some of its normal and abnormal relations cannot fail to aid us in the study of the aberrations of the human mind. The causes of sleep, when thoroughly studied, will be found to have a distinct bearing on the therapeutics of wakefulness and of insanity. The state of the mind during sleep is analogous in some respects to that which exists in some forms of lunacy. Dreams, both healthy and morbid, are sometimes the starting point of insanity, and often play an important part in its clinical history. Wakefulness is frequently either the obvious cause of mental alienation, or the first sign that the mind is beginning to waver from its normal standards; and the pathology of this condition throws more light on the pathology of the subsequent state of mental darkness into which the individual passes. I am very sure, therefore, that, in asking the attention of the reader to the chapters in this section, I am rendering a service both to him and the unfortunate persons who may come under his medical charge. CHAPTER I. 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,' 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 fibres, or rather in a partial motion in these fibres. 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 influences 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 brow; 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 1 "Du sommeil, des rêves et du somnambulisme," etc., Lyon, 1857, p. 14. 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,' 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' 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' declares that a "degree of pressure is essential to perfect and uniform sleep." Dr. Dickson 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' 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 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 declares that as soon as the necessity for sleep 1 "Observations in Medicine," second series, p. 27. "Cyclopædia of Anatomy and Physiology," art. "Sleep," vol. iv, part i, p. 681. "Chapters on Mental Physiology," London, 1852, p. 105. "Essays on Life, Sleep, Pain," etc., Philadelphia, 1852, pp. 63, 64. "Nouveaux éléments de la science de l'homme," 3me édition, Paris, 1858, vol. ii, p. 7, et seq. 7.66 Rapports du physique et du morale de l'homme," Paris, 1824, p. 379. 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,' 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' 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." The theory that sleep is due directly to pressure of bloodvessels, 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 1 "The Physiology of Common Life," New York, 1860, vol. ii, p. 305. "Philosophy of Sleep," second edition, 1850, p. 5. "The Haven of Health, chiefly made for the comfort of Students, and consequently for all those that have a care for their health," etc. By Thomas Cogan, Master of Arts and Bachelor of Physic, London, 1612, p. 332. other physiological truths, distinctly announces it in his "Christianismi Restitutio," when he says: "Et quando ventriculi ita opplentur pituita, ut arteriæ ipsa 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 chief 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,' 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 bloodvessels 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. "Sketches of the Philosophy of Life," London, 1819, p. 262. |