Why Do We Sleep - Part two ?
Recently, however, a decided advance has unquestionably been made in our understanding of this fundamental fact in the life both of man and of the lower animals. It is an advance due in part to the progress of biological and physiological research, but even more due to the extraordinary development of that youngest of the sciences, psychology, which in the past few years has made so many important contributions to the fund of human knowledge. Not a few of these, it is worth noting, have wholly or partly originated from the increased attention that the modern psychologist has paid to the realm of sleep.
Our present appreciation of the marvelous extent to which one's intellect, one's character, and even one's health are affected by "subconscious" emotions and memories; our appreciation of the formative influence of the most trivial details in one's environment, and of the possibility of adjusting the environment in such a way as to make unfailingly for physical, mental, and moral upbuilding; our fuller comprehension of the principles that underlie and give validity to scientific "psychotherapy," or healing by suggestion, of which the medical fraternity is beginning to make systematic and effective use — all this has been largely due to recent psychological study of the phenomena that occur either in ordinary, "natural" sleep, or in those allied sleeping states induced by drugs or hypnotic procedures.
Naturally enough, from studying the phenomena of sleep, the investigators have been led to study sleep itself, with results which, if they do not altogether dispel its mystery, have at least afforded clearer insight than ever before into its nature, significance, and causal conditions — matters of considerable practical as well as theoretical importance, particularly in this age of stress and strain with its imperative demand for the most efficient utilization of human resources, and its equally inexorable tax on the human organism.
The great difficulty has always been to formulate an explanatory hypothesis which — excluding the various types of pseudo- sleep that manifestly result from abnormal conditions — would adequately account for the many strange anomalies presented by sleep. Any hypothesis to be satisfactory has to explain, for example, why sleep predominates over waking life in the case of the very young, why it has a smaller share in middle life, and why it tends in old age to become dominant once more, or, with no ill effects, to be even less in evidence than in the years of greatest virility.
Any sound theory has to explain the seeming paradox between the periodical onset of sleep after exertion and its frequent withdrawal when the exertion has been at all excessive. It has also to explain the well- established fact that the amount of sleep required is by no means proportionate to the amount of intellectual or muscular effort previously expended, so that we often find men of intense mental or physical activity — for instance, Napoleon, Frederick the Great, Schiller, Humboldt, Mirabeau, the English surgeon John Hunter, and our own Thomas A. Edison — getting along very well with four or five hours' sleep a night, as compared with the eight or nine hours of less energetic individuals.
Then, too, there is the familiar and most embarrassing occurrence of sleep in public places — the church, the theater, the opera-house — on the part of persons suffering neither from fatigue nor from any interruption to their regular night's rest; and, opposed to this, the chronic wakeful- ness of the insomniac in the dark and quiet of his home, utterly worn out yet unable to sleep.
These are only a few of the puzzling phases that have to be accounted for, and that have combined to baffle until now all efforts at a consistent and comprehensive explanation of sleep. But with the development of modern psychology, and, above all, with the increased appreciation it has enforced of the preponderating influence of the psychical factor in all aspects of human existence, real progress towards such an explanation has, as was said, been made.
It is now known that sleep, contrary to the belief formerly so widely entertained, is no mere passive, negative state, the product of toxic or other harmful elements, but is an active, positive function, a protective instinct of gradual evolution and dependent for its operation partly on the will and partly on the environment. It is the result of a certain reaction between the central nervous system and the stimuli impinging on it, its object being not so much the recuperation of the organism from the effects of the activities of the intervening period of waking life, as to save the organism from the destructive consequences of uninterrupted activity.
Or as one investigator, Doctor Boris Sidis, the well-known American medical psychologist, affirms:
"Sleep is not a disease, not a pathological process due to the accumulation of toxic products in the brain or in the system generally. Sleep is not an abnormal condition; it is a normal state. Like the waking states, sleep states are part and parcel of the life-existence of the individual. Waking and sleeping are intimately related — they are two different manifestations of one and the same life-process — one is as normal and healthy as the other. One cannot help agreeing with Claperede's biological view that sleep is a positive function of the organism, that sleep belongs to the fundamental instincts.
As Claperede forcibly puts it:
"'Sleep is a protective function, an instinct having for end, in striking the animal with inertia, to prevent it from arriving at a condition of exhaustion. We sleep, not because we are poisoned or exhausted, but so that we shall be neither poisoned noi> exhausted.'"
To be continued...