In dismissing this subject I desire to caution against a routine employment of this so-called rest-cure, which might readily degenerate into a species of quackery; and, again, to call attention to the widespread value of the principles which underlie it, and the importance of the physician applying those principles with endless modifications of detail.
SLEEP, AND ITS DISORDERS.
BY HENRY M. LYMAN, A.M., M.D.
The regularly-recurring incidence of natural sleep forms one of the most important subjects of physiological investigation. Occurring ordinarily at stated intervals connected with the diurnal revolution of the earth, it may for a time be postponed by an effort of the will, but an imperious necessity for repose finally overcomes all opposition, and the most untoward circumstances cannot then prevent the access of unconsciousness. Thus produced, the relation of cause and effect between weariness and sleep becomes very apparent. The refreshing influence of such repose points clearly to the restorative character of the physical processes that continue despite the suspension of consciousness; it also renders evident the final cause of that periodical interruption of activity which the brain experiences in common with every other living structure.
Careful observation of the manner in which sleep invades the body indicates that its evolution is not associated with a simultaneous suspension of every mode of nervous function. The sense of sight is the first to yield. The eyelids close and the muscles that support the head give way. The body seeks a recumbent position; quiet and seclusion are instinctively sought. The purely intellectual faculties are not yet depressed, and the reflex energies of the spinal cord are exalted. Soon, however, the other senses fail; hearing persists the longest of all. Released from the control of external impressions, the internal senses preserve their functions after a strangely-disordered fashion, dependent upon the progressive suspension of activity in the various cerebral organs. First the power of volition ceases; then the logical association of ideas comes to an end. Presently the reasoning faculties disappear, and judgment is suspended. We thus become no longer capable of surprise or astonishment at the vagaries of memory and imagination, the only mental faculties that remain in action. To their unrestrained function we owe the presentation in consciousness of the disorderly picture which we call a dream. During the early stages of this somnolent state we often remark the fact of dreaming, and an effort at attention may produce a partial awakening; but usually the subsidence of cerebral function is progressive and rapid. The fire of imagination fades; the field of consciousness becomes less and less vividly illuminated; the entire nervous apparatus yields to the advancing tide; and, finally, the dominion of sleep is fully confirmed.
During the act of awaking the order of sequences is reversed. From the end of the first hour of repose the depth of sleep, at first rapidly, then more gradually, diminishes.1 Dreams disturb its quiet, mental activity increases, the power of volition revives; once more the individual is awake.