(2) Sex.—Women have been stated to require rather more sleep than men, but this is doubtful. The hours of sleep required have in accordance with this view been stated to be, “Six for a man, seven for a woman, and eight for a fool.” A reversal of this order would more nearly approximate to the requirements of town life.
(3) Temperament.—Those of a cold lymphatic temperament require more sleep than sanguine or nervous people, though the latter sleep more deeply. Frederick the Great, John Hunter, and Napoleon I. are said to have required only five hours’ sleep per day; but the last of these had the faculty of taking short naps at a few moments’ notice.
(4) The sick and convalescent require much more sleep than those who are healthy.
(5) Habit has a very important influence. Many people appear to sleep too much, and thus dull to some extent their mental faculties; but on the other hand, modern life, with its nervous strain, keen competition, and constant hurry and worry may make a larger amount of sleep necessary than that required by our forefathers, who invented the foregoing proverb.
(6) Occupation.—Mental work requires more repose than physical.
2. Relation of sleep to food.—The molecular life of the tissues—that is, the processes of nutrition—ought to be undisturbed. These go on most perfectly when no active function, such as that of digestion, is being performed. But while the stomach carries on the digestive functions to only a small extent during sleep, the intestines continue still to digest and absorb food. In accordance with these facts, it is advisable to allow at least two hours between the last meal of the day and sleep, especially if animal food has been taken.
3. As absorption is increased and the temperature is lowered during sleep, it is important to sleep in pure air, and to have warm coverings, especially about the shoulders and arms. Many an obstinate cough might be cured by the simple expedient of wearing a flannel jacket at night.
4. Sleep during the night and not during the day. It should hardly be necessary to say this, as the universal instinct of animals shows its advisability; but, unfortunately, the habits of mankind have commonly led to a partial reversal of the natural arrangement.
5. The room should be dark; light, like sound, is inimical to sleep. The head should be moderately raised. The temperature of the room for robust persons need not be artificially raised.
Sleeplessness, as a rule, occurs only when some physiological law has been broken. To relieve it, it is essential to equilibrate muscular and mental functions. Increase of muscular exercise is an important element in its treatment. In addition it is advisable not to have any severe mental work during the evening, nor to indulge in late suppers. Sleeplessness is the bane of many men of a nervous temperament, and chiefly attacks those of sedentary habits. It is apt to recur, and for this reason, if for no other, narcotics ought to be scrupulously avoided. The habit of taking such soporifics is unfortunately becoming much more common, and is productive of many evils. Death from accidental overdose is a frequent calamity; and, apart from this possibility, the invalid’s nervous system is completely ruined by persistence in the habit, his power of will is annihilated, and he becomes the miserable slave of an evil habit, whose end is death (see also page [54]).