*Exercise as a Counteractive Agent.*—In counteracting tendencies to disease and in the maintenance of the functional equilibrium of the body, no agent has yet been discovered of greater importance than physical exercise, when applied systematically and persistently. This may consist of exercises that call into play all the muscles of the body, or which are concentrated upon special parts. When general tonic effects are desired, the exercise should be well distributed; but when counteractive or remedial effects are wanted, it must be applied chiefly to the parts that are weak or that have not been called into action by the regular work. Unfortunately, health is sometimes confused with physical strength and exercise is directed toward the stronger parts of the body with the effect of making them still stronger. Not only is health not to be measured by the pounds that one can lift or by some gymnastic feat that one can perform, but the possession of great muscular power may, if the heart and other vital organs be not proportionally strong, prove a menace to the health. This being true, one having his health primarily in view will use physical exercise, in part at least, as a means of building up organs that are weak. Since the body, like a chain, can be no stronger than its weakest part, this is clearly the logical method of fortifying it against disease. *Value of Work.*—Although there may exist in one’s vocation certain tendencies to disease, it must not be inferred that work in itself is detrimental to health. Health demands activity, and those forms of activity that provide a regular and systematic outlet for one’s surplus energy and compel the formation of correct habits of eating, sleeping, and recreating best serve the purpose. Work furnishes activity of this kind and serves also as a safeguard against the unhealthful and immoral habits contracted so often from idleness. Even physical exercise which has for its purpose the reënforcement of the body against disease may frequently consist of useful work without diminishing its hygienic effects. *The Mental Attitude.*—While a proper thoughtfulness and care for the body is both desirable and necessary, it is also true that over-anxiety about, or an unnatural attention to, the needs of the body reacts unfavorably upon the nervous system. Observance of the laws of health, therefore, should be natural and without special effort—a matter of habit. The attention should never be turned with anxiety upon any organ or process, but the mental attitude should at all times be that of _confidence in the power of the body organization to do its work_. Fear and morbidity, which are disturbing and paralyzing factors, should be supplanted by courage, cheerfulness, and hopefulness.