The sleepy feeling caused by fatigue is due to the circulation in the blood of toxins resulting from tissue waste, which benumb the brain-cells; while the feeling of freshness and _bien-être_ with which one awakens in the morning is due to the elimination of the fatigue products from the blood during sleep. If the blood of a tired dog be transfused into the veins of a perfectly fresh animal, the latter will immediately show symptoms of somnolence and seek a dark corner for sleep. The medical authorities of to-day are pretty well agreed that eight hours of sleep is the minimum required for the maintenance of health, and all concede that the brain-worker requires more sleep than the manual laborer. Every moment after the feeling of languor presents itself is a strain upon the nerves and muscles which will sooner or later invalidate for life, and finally bring the victim to a premature grave. Habitual deficiency of sleep will undermine the strongest constitution. It is a matter of great importance to train one’s self in the habits of sleep, regularity in the hour of retiring, abstinence from active brain work for the hour immediately preceding going to bed, since, if active brain work is continued until one goes to her room for the night, the chances are that the brain will continue its activities after getting into bed, and sleep may be banished from the pillow for several hours. A few minutes spent in breathing exercises, the vigorous use of the flesh brush or hair glove, a hot plunge or foot-bath are no mean hypnotics. A sound sleep is dreamless. Dreams require a certain expenditure of nerve force and mental energy, so that dreamless sleep is the most restful. Disagreeable dreams and “night-mares” are generally associated with indigestion and biliousness, which also occasion a general restlessness. All this can be overcome by taking some medicine for the liver. Two grains of calomel taken just before retiring often works like a charm. The dose must not be repeated under a month. In case of tendency to insomnia, no coffee should be taken after breakfast. =Treatment of Insomnia.=—The mechanical measures for the relief of insomnia have for their purpose the withdrawing of the blood from the brain to the surface of the skin. Hot foot-baths; general warm baths; cold douches to the spine, brisk exercise; light massage, and cold rooms. Mental work should be laid aside several hours before retiring; late suppers avoided; coffee, if taken at all, should only be taken for breakfast, and then only one cup. Reading or amusement should be selected that does not excite the nerves. To woo sleep the woman should put herself in a position of rest, which of itself physiologically induces sleep. Avoid irritations, noises, bad air, cold feet, overloaded bowels, all of which tend to wakefulness and to prevent the proper physical rest. Then sleep usually comes of itself.