Habitual overwork produces fag and a desire for stimulants to act as a spur to the overworked muscles during the day, and recourse to increased stimulants or sedatives to act as hypnotics at night. The inert nerve-centers have no reserve energy to give out, so it is worse than useless to stimulate them. On the other hand, the nerve-centers are at too low an ebb to react from the depressing effects of sedatives, which, to the individual, must be positively injurious. The aim must be to promote nutrition, and to give complete rest to the exhausted nerve-centers. Brain work, to be beneficial, must be regulated with the greatest care. During the exercise of the brain there is always an increased blood-supply to it. If the exercise is continued too long, there is a tendency for the blood to remain in too great quantity, due to the exhaustion of the nerve-cells, which are no longer able to control the vessels. During sleep the blood-supply to the brain is diminished and the cells recover themselves, but if this hyperemia be persistently kept up, sleep soon becomes impossible, the brain-cells have no opportunity to become repaired, and their activity is diminished. Richardson says: “Making all allowances for differences, even in the prime of their mental and physical vigor, few individuals can exceed six, and for most persons prudence would direct not more than four or five hours of close mental application, without seriously endangering their health.” No real advantage is gained by eight or ten hours of daily study, since the memory and reasoning powers become so exhausted that the assimilation of ideas becomes slower and more difficult. When in his prime, Walter Scott declared that six hours a day was all that he could profitably spend upon his literary compositions. In later years, because of his pecuniary embarrassment, he worked beyond this limit, and, as the result of excessive labor, his last years were spent in hopeless imbecility. =Signs of Overwork.=—These show themselves in irritability, with a sense of exhaustion, the irritability being due to an exhaustion of the nerve-centers. Work becomes irksome. There are periods of depression and melancholia, which recur at shorter and shorter intervals and continue for a longer period of time. There is a slight loss of memory, together with inability to concentrate the mind upon any given subject for any considerable length of time, and the power of thought and judgment are impaired. There are sleepless nights, ringing in the ears, fatigue from the slightest exertion, an irregular action of the heart, with palpitation and a frequent desire to urinate. Various forms of pain and neuralgia occur.