which suffers most, while in deprivation of food it is the brain which preserves longest the integrity of its structure and function. In young animals, abundantly fed and cared for but kept awake, there follows serious lesions of the organism which soon become irreparable, and death results.
There have been many theories and hypotheses advanced to explain the phenomena of somnolence. The physiologists have here, as so frequently elsewhere, exhibited far more academic than practical interest in the matter. There is no subject, however, of greater importance, since it is a prime factor in all the reparative phenomena of life, standing at the foundation of nutrition; yet no research work has been done on the nature of sleep commensurate with the gravity of the subject. Psychologists have written extensively on one phenomenon of sleep, viz., dreams. Normal sleep has attracted so little attention that we do not know exactly how to modify it in accordance with common conditions of bodily derangements. Inferentially certain facts seem established which not only account for the phenomena of sleep, but enable us to reason from them and thus to regulate the state in great measure; sometimes sufficiently. It is probable that during sleep there is a diminished resistance in the surface vessels, inducing lowered blood pressure, hence smaller amounts of blood pass through the brain. As sleep approaches the cerebral vessels grow relatively less filled with blood for an hour or more after full somnolence has come. After reaching its minimum tension the brain circulation remains practically constant for one or two hours or more, gradually returning to normal as the time for awakening nears.
After having attained a fair idea of what sleep is, whereby we can better appreciate a reasoning from our individual standpoint, we may proceed to discuss its regulation. For the young, who may be assumed to be in possession of full neural and circulatory balance, whether in or out of health, the regulation of sleep is a simple matter, one which will in most instances adjust itself if the subject be placed under normal conditions.
We may fix our attention most profitably upon the status of sleep in those of middle or late life. Here a number of causes conspire to disturb equilibrium of body cells, sometimes slightly, and at others it will be found that effects have been insidiously wrought which may suddenly obtrude upon our attention, causing great distress, often impairing the integrity of our judgment, hence our working efficiency. Therefore a double peril assails. Mere inability to sleep naturally, or as heretofore, or as each one assumes as a right, is, especially among men (who shrink from admission of physical weakness), seldom regarded as worth their seeking the advice of a physician. Whereupon the simplest remedy is to hunt about for something which will obtund
