HOW SLEEP IS PRODUCED

Timaru Herald, Volume CXXXVII, Issue 19451, 28 March 1933, Page 2

HOW SLEEP IS PRODUCED

LIGHT ON OLD MYSTERY. The problem of sleep Is one that has fascinated thinkers since the beginning of history. It has been studied from every possible angle. In the exact sense, however, hardly anything has yet been known of the actual bodily processes by which sleep is produced (writes the Medical Correspondent of the "London Daily Telegraph”). Particular interest, therefore, is attached to the brilliant investigations of Professor W. R. Hess, the physiologist of Zurich University, a summary of which has been published in the ’Lancet.” As Professor Hess pointed out. the obvious facts of sleep are the cessation of functioning of the sense organs and complete relaxation of the voluntary muscles engaged in waking activity. On the other hand, the unconscious functions of the body continue. Though lessened in rate, the heart continues to beat, and the lungs to expand and contract. The processes of digestion are carried on. Now just as our intelligent activities are dependent upon the cortex of the brain and the elaborate nervous system that has been evolved to subserve them, so these purely involuntary functions are controlled by a more primitive but not unconnected nervous system, known as the sympathetic. Slowing Down thfe Heart. This sympathetic system has been shown to have a peculiarly close connection with what are kpown as the endocrine glands. These glands, such as the supra-renal (capping the kidneys), the thyroid (in the neck) and the pituitary (in the skull), produce internal secretions or hormones of the utmost importance. They are intimately associated with the emotions, such as fear and anger and their effects.

Acting in connection with these glands, the sympathetic nervous system is responsible for keeping the body in a state of preparedness for the demands that its waking intelligence has

to meet. But there is a small portion of it, known as the para-sympathetic, that acts somewhat differently. Its function Is inhibitory. It can slow down the heart and contract the pupil of the eye. It is in the nature, in fact, of a brake that helps, in times of stress or undue fatigue, to conserve valuable energy. It is to this para-sympathetic part of our primitive nervous system that Professor Hess assigns the responsibility for sleep. Professor Hess has found that, by the injection of a substance that stimulates the inhibitory para-sympathetic nerves, he can induce a condition in animals that is indistinguishable from normal, natural sleep. He has also found that he can bring about the same result by electrically stimulating certain deep-lying areas of the brain, known on other grounds to be closely associated with this primitive nervous system. Although he is not prepared to say that he has definitely established the existence of a sleep centre in the brain, other workers are convinced that this can now be deduced.

Finally Professor Hess refers to some extremely interesting observations of Zondek and Bier, of Berlin. The.se workers have found by experiment that the bromine contents of the pituitary endocrine gland are emptied during sleep ’into a certain portion of the rtem of the brain. The gland refills again before the act of waking. They thus suggest the presence of a definite sleep hormone, or internal secretion.

This theory must await further confirmation. But both this work and that of Professor Hess would appear to have marked a very definite advance in our knowledge of one of the most mysterious processes of our everyday life.