ABSTRACT
Like a great river flowing through a city, the sleep instinct flows gently but powerfully through our lives. The desire to sleep is a motive which can be just as strong as the desire to eat or drink, even though psychologists rarely include it in their list of drives. One of the brain's many jobs is to assign priorities, to decide which problems will be tackled first. It is tempting to assume that the desire to sleep arises from the fatigue associated with prolonged waking activity. Man is not the only animal in creation to spend many hours each day in a state of semi-conscious immobility. The view that sleep is actively controlled by the central nervous system has one very surprising but important implication. It is proposed that we all carry in our heads a sleep control mechanism whose action is timed by internal clocks which trigger off feelings of drowsiness and fatigue at certain times of day.
