Many a college youth, endowed by Nature with a sound physical body and a healthy brain, has irreparably injured both by sitting on the end of his spine with his feet higher than his head, poisoning his blood with tobacco narcotics from a stylish pipe and failing to keep it purified by obeying the laws of motion and of oxidation. Constructive exercises should employ every muscle in the body long enough once in every twenty-four hours to generate sufficient heat to cause perspiration, or at least to force twice the normal quantity of blood to the lungs for purification. Exercise thus taken up to the point of fatigue, and of sufficient duration to use all the nutrition taken in the form of food, will, under favorable conditions, build the body to its highest degree of physical strength, provided we keep Nature supplied with the right kind of material (food) with which to do her work. EXERCISE FOR REPAIR [Sidenote: In mature life exercise only for repair] After the body has reached maturity, or attained its full growth, the only exercise needed is for repair. This it must have or Nature will inflict her inexorable sentence in some form of congestion. [Sidenote: Why the "trunk" requires exercise] In various industrial and professional pursuits the legs, neck, and arms are used enough to keep them in a fair state of repair. That part of the body, therefore, that suffers most for want of motion, or exercise, is the trunk. In this part of the anatomy are located the vital organs controlling not only the circulation and the oxidation of blood, but also those organs upon whose normal action depend solely the questions of digestion, assimilation of food, and elimination of waste. [Sidenote: If properly nourished the body will demand a certain amount of exercise] If the food is selected, combined, and proportioned so as to produce chemical harmony in the stomach, and to meet the requirements of age, temperature of environment, and work, the body will be kept sufficiently charged with energy to demand a certain amount of exercise. If the command is obeyed the body can be trained to work automatically, as it were, but where the vocation is sedative, or prevents obedience to these demands, the trunk should be exercised in the open air from thirty to forty minutes daily by flexing, tensing, twisting and bending in every possible way, long enough and rapidly enough to double the normal heart action and inhalations of air. PHYSIOLOGY OF EXERCISE [Sidenote: Necessity of motion for body development] By motion (exercise) the muscles are stimulated in growth, becoming larger and more firm, thus giving strength and symmetry to the body. Food, without proper motion, will not develop muscular tissue to its highest degree. Exercise must be taken to stimulate the growth of the tissues forming the muscle-cells. Among the benefits derived from exercise, the following may be noted: [Sidenote: Growth produced by exercise]