Why Do We Sleep?
SLEEP has long been regarded as one of the most baffling of the many knotty problems that science has been called upon to solve.
The scientist, of course, in common with the layman, has always recognized and appreciated its essentially beneficent character, so happily expressed in the words of the immortal Sancho Panza, "Blessings on him who invented sleep ! - the mantle that covers all human thoughts ; the food that appeases hunger; the drink that quenches thirst ; the fire that warms ; the cold that moderates heat; and, lastly, the general coin that purchases all things; the balance and weight that make the shepherd equal to the king and the simple to the wise."
But, while recognizing the kindly and restorative role played by sleep in the scheme of animate existence, the scientist almost as much as the layman, until lately at all events, has been in the dark with respect to its nature and mechanism.
Even the conditions that determine its production have been but vaguely and partially understood, with the result, as every doctor knows, that sleeplessness still constitutes a great stumbling-block in medical practice. Science, in fact, has quite generally been content with describing the phenomena of sleep, as one may readily ascertain by examining the now voluminous literature on the subject.
Even when explanations have been attempted, they have usually resolved themselves into descriptions of states that accompany sleep rather than demonstrations of the factors that cause it. Thus, the investigations carried on by Durham, Hammond, Howell, Mosso, and others, alleged to prove that cerebral anaemia, or deficiency of blood in the brain, is the great cause of sleep, really prove nothing more than that certain circulatory changes take place during sleep.
Or if the theories advanced are truly explanatory - as is the case with the chemical and pathological theories which attribute sleep to a poisoning of the system by toxic substances that accumulate in the blood - they suffer from the serious objection that sleep often occurs under conditions in which the factors stressed cannot reasonably be assumed to have a part.
Small wonder, therefore, that many writers have ventured on nothing more than an elaboration of the obvious, like Marie de Manaceine, the Russian authority, whose theory of sleep is summed up in the distinctly non-explanatory phrase : "Sleep is the resting-time of consciousness."
To Be continued......
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