Chapter XVII

The natural duration of sleep is eight hours out of the twenty-four, and those who can secure this lead the soundest lives. It is best taken from ten o'clock till six, and it is most readily obtained by cultivating it as an automatic procedure. All stimulants, all excitements, all excessive fatigues, all exhaustions pervert sleep even if they do not prevent it. The room in which sleep is taken should be the best ventilated and the most equably warmed room in the house. The air of the room should be maintained at the natural standard of 60° Fah., and the body of the sleeper should always be kept completely warm. The bed should be soft and yielding. A regular tendency to sleep at other hours than the natural is a sure sign of error of habit or of nervous derangement.