=Brain Worry.=--"After a good spell of hard work, the brain worker is often tormented by finding it difficult, all at once, to turn off the steam. His work-day thoughts will intrude themselves in spite of every effort to keep them out. Thackeray generally succeeded in exorcising the creatures he had been calling into existence, by the simple expedient of turning over the leaves of a dictionary. A great lawyer was in the habit, in similar circumstances, of plunging into a cold bath, and averred that a person never took out of cold water the same ideas that he took into it. Perhaps the best mental corrective of this condition is to employ the mind for a short time in a direction most contrasted to that in which it has been overworked. During excessive labor of the brain, there is an increased flow of blood to the working organ. If this condition of distention is long continued, the vessels are apt to lose the power of contracting when mental activity is diminished. Hence arises the impossibility of fulfilling the physical conditions of sleep, the most important of which is the diminution of the flow of blood to the brain. It is certain enough that the continued deprivation of any considerable part of the normal amount of sleep will be seriously detrimental to health. Dr. Hammond, in his work on sleep, mentions the case of a literary man in America who for nearly a year restricted his rest to four hours a day, and frequently less. At the end of that time, the overtasking of his mental powers was manifested in a curious way. He told the physician that, though still able to maintain a connected line of reasoning, he found that as soon as he attempted to record his ideas on paper, the composition turned out to be simply a tissue of arrant nonsense. When in the act of writing, his thoughts flowed so rapidly that he was not conscious of the disconnected nature of what he was writing, but as soon as he stopped to read it over, he was aware how completely he had misrepresented his conceptions." =Breathing.=--In each respiration an adult inhales one pint of air. A man respires 16 to 20 times a minute, or 20,000 times a day; a child, 25 to 35 times a minute. While standing, the adult respiration is 22; while lying, 13. The superficial surface of the lungs, _i. e._,of their alveolar spaces, is 200 square yards. The amount of air inspired in 24 hours is about 2,500 gallons. Two-thirds of the oxygen absorbed in 24 hours is absorbed during the night hours, from 6 P.M. to 6 A.M. Three-fifths of the total carbonic acid is thrown off in the day-time. The pulmonary surface gives off about 5 fluidounces of water daily in the state of vapor. The heart sends through the lungs 192 gallons of blood hourly, or 4,608 gallons daily. The duration of inspiration is five-twelfths, of expiration seven-twelfths, of the whole respiratory act; but during sleep, inspiration occupies ten-twelfths of the respiratory period.