WHAT IS SLEEP?

Manawatu Herald, Volume XLV, Issue 2540, 8 February 1923, Page 1

WHAT IS SLEEP?

(By a Physician)

Although it is more necessary to life than fool, we must confess that up to the present the exact cause of sleep is not definitely known. Careful observation has made us familiar with the physical eonditkji of the body during sleep, and from this it would appear that it is a condition of debility. Thus although no physical or mental function is absolutely abeyant all the normal activities of the organism are appreciably lowered. The blood pressure is lower, the heart beats more slowly, respiration is slower and less deep and the amount of air inspired by a normal man during sleep is only one-seven-th of that used during similar periods of quiet wakefulness. The chest and limbs usually increase in size during sleep owing to changes of circulation which facilitate the passage of fatigue products into the blood stream. There is certainly an increased vaseularly of the skin, which is often flushed and the brain left with less blood is comparatively anaemic. It is owing to the increased action of the skin that we are so easily chilled during sleep. It is when we come to consider the tate of the cells in the brain during sleep that we are baffled and conjecture must take the place of certainty. The grey matter of the brain is composed and linked together by fine nerve fibres. These cells receive sense-impressions from all over the body, and, after interpreting them, send out controlling messages. When we try to realise that in a normal brain there, are more than 9,000 millions of such cells, all linked up together, we gain some idea of the complexity of this wonderful nerve mechanism. Each of these cells is provided with fine branching fibres which on account of their tree-like appearance are called “dentrites —from the Greek word “dendron” a tree. It is believed that these fine, branching fibres have much to do with sleep, but the exact way in which they accomplish it is not known. It is thought probable that they either retract leaving a space which cuts off nerve currents, or, conversely, that they become more intimately connected, causing a general diffusion of nerve energy. Either of these conditions would favour and induce sleep. It is, however, as well to remember that the real changes may after all, be in the nerve cells themselves, for when a tree begins to wither the earliest signs are noted in the smallest branches, although the seat of mischief is probablv in the root.