4. THE HYGIENIC REQUIREMENTS OF SLEEP.
The personal hygiene of sleep is by no means an unimportant topic, though it may be briefly treated.
The amount of sleep that each individual requires and should take can only be determined by the individual. Some seem to require ten hours, others eight, others six, while rarely individuals are found who seem to thrive on even so little as five hours of sleep out of twenty-four. The average requirement seems to be about eight hours. If one has by experience or experiment determined the amount of sleep which he requires, he should so plan his daily regime that he can secure that amount of sleep. While a brief departure from this regime may be without serious results, any prolonged departure from it will certainly bring its natural retribution. So, the young man having determined how much sleep he needs, should adopt a daily program that will provide for just that many hours in bed, and he should early establish the habit of going to sleep at once upon retiring, and of arising at once upon awakening. Dallying in bed has led many a young man to lapse into habits of thought and of action that are in a high degree deleterious, morally and physically.
So far as one may choose the equipment of his sleeping apartment, he should choose a hard bed and a cover as light as possible and yet be comfortable.
One should never retire with cold feet. A most effective way to warm the feet is to dip them for a moment in cold water and then rub them vigorously with a coarse towel until they glow with warmth. Furthermore, no more effective remedy for habitual cold feet could be devised than this nightly tonic bath.
One will add greatly to his comfort and decrease largely the danger of taking cold if he provides himself with a pair of warm bed room slippers, which should always be worn during one's excursions to the bath room, and during his tonic sponge bath.
As to posture in bed, the experience of men in general is, that the most comfortable posture and the most hygienic one is to lie upon the side. The right side is to be preferred to the left because in this position, the heart being on the upper side, is not embarrassed in its free movement by the superincumbent lung tissue. Furthermore, this position facilitates the passage of digesting foods from the stomach. To maintain comfortably this side position, requires that the knees be at least moderately drawn up. This posture when asleep is practically identical with that of nearly all higher animals, and is unquestionably the most hygienic one for man. No animal but man ever lies upon its back unless it is dead. Furthermore, the dorsal position puts tendons, nerves and muscles on a stretch, while the flexed lateral position puts these in a more or less relaxed position, which is most favorable to rest.
It goes without saying that sleeping rooms should always be thoroughly ventilated. The occupant should take care that he does not lie in a direct draught from a window or door, because it has been found by experience that one is less likely to catch cold if he sleeps out of doors than he is if he sleeps in a direct draught from a window or door. Just why this is has not been satisfactorily accounted for, but the fact remains. So if you must sleep in the house, secure perfect ventilation without direct draughts.