When our side of the globe turns away from the sun, we close our eyes and go to sleep in the darkness of night. Even the green plants shut down some of their daytime occupations and most of the animals also sleep through the night. Life, it seems, must be divided into busy spells of waking and quiet spells of sleep, for the animals that prowl by night must doze through the day. The reason why we must sleep is still much of a mystery and science cannot yet give us all the answers.

Some suggest that we must sleep to rest the busy nervous system and the brain. Maybe the nervous system becomes overloaded like a crowded switchboard. This may or may not explain why sleep is necessary, but one thing is certain. The human body cannot keep going for more than a few days and nights without sleep and even the healthiest person becomes sick without regular sleep.