Sleep is one of nature's greatest inventions and blessings of life. It is a periodic rest of the body which is absolutely essential for its efficient functioning. It has been called " most cheering restorative of tired bodies. "

Sleep is the indispensable condition to the recuperation of energy. We go to bed fatigued and get up refreshed. Sleep repairs the wear and tear of the body and mind incurred during waking hours. Nothing is so restorative to the nerves as sound and uninterrupted sleep. Sleep is thus a vital element in a total way of life. It is a basic need in man's mental as well as physical life.

During sleep most of the functions of the body are carried on at the lowest level possible in health. Heat production is from 10 to 15 per cent below the basal level. The mechanism regulating the body temperature are less sensitive than in the waking state and are depressed by 0.5 to 1.0 degree F. The rate of the heart is reduced by 10 to 30 beats per minute and a decline in blood pressure of about 20 mm occurs in quiet restful sleep. The urine volume is considerably reduced, but its concentration in solids is increased. The tone of all the skeletal muscles is lessened. The eyes are usually rolled upward and the pupils constricted.

Loss of sleep exerts seriously detrimental effects upon the nervous system. Long periods of wakefulness may cause profound psychological changes such as loss of memory, irritability, hallucination and even schizophrenic manifestations. During the last World War, prisoners in Nazi concentration camps who kept awake for days by strong lights and blaring wireless sets, collapsed.