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Rh still more to lack of precision in its application. While its proper prescription is undoubtedly more difficult than that of drugs, no drug is capable of producing effects at all comparable, and the care and attention devoted to its intelligent application by physician and patient are well repaid. It is a practical point of the first importance that individuals differ enormously—according to constitution, temperament, training, and previous habits—as to the amount of exercise that will be required to produce a given result. While those who have been trained may require severe or laborious exercise to produce physiological effects, the writer has met with individuals free from disease in whom the gentlest passive movements, lasting the fraction of a minute, would produce decided subsequent stiffness and constitutional disturbance. As it is just these sensitive and undisciplined people who may be most benefited by properly adapted exercise, it is evident that the kind and amount required must not be gauged by any absolute standard but by the reactive powers of the individual. Like some drugs, exercise may produce different and even opposite effects, according to the dosage and consequent intensity of action. Slow rhythmical passive movements are decidedly calming, while moderately active movements are stimulating to mental action. A careful distinction should be made between primary and remote effects. Exercise has also its synergists, antagonists, and incompatibles, its acute and chronic toxic effects, and their antidotes. The synergists of exercise are fresh air, a nourishing diet, sufficient rest, an unstrained and cheerful mind, and temperate and regular habits; moderate cold and possibly certain tonic drugs are a help to exercise. Exercise is antagonized by the opposite of the above-mentioned, and by toxic substances in the blood. Some interesting facts have recently been observed as to the effect of the use of tobacco in checking growth and the developing effect of exercise. From measurements of the one hundred and eighty-seven men of the class of 1891, Yale, Dr. J. W. Seaver found that the non-users of tobacco gained in weight during the college course 10·4 per cent more than the regular users, and 6·6 per cent more than the occasional users of tobacco. In height the non-users increased twenty-four per cent more than the regular users and twelve per cent more than the occasional users. In increase of chest girth the non-users had an advantage of 26·7 per cent and twenty-two per cent, and an increase of lung capacity of 77·5 per cent and forty-nine per cent respectively. These facts in regard to the dwarfing effects of tobacco are corroborated by observations on the class of 1891, Amherst, made by Dr. Edward Hitchcock. He found that in weight the non-smokers increased during their course twenty-four per cent more than the smokers; in increase in height they surpassed them thirty-seven per cent;