*The Problem of Increasing One’s Energy.*—Since the energy supply is kept up through the food and the oxygen, it might be inferred that the introduction of these substances into the body in larger amounts would increase the energy at one’s disposal. This does not necessarily follow. Oxidation at the cells is preceded by digestion, absorption, circulation, and assimilation. It is followed and influenced by the removal of wastes from the body. A careful study of the problem leads to the conclusion that while the energy supply to the body does depend upon the introduction of the proper amounts of food and oxygen, it also depends upon the efficiency of the vital processes. The maximum amount of energy may, therefore, be expected when the body is in a condition of perfect health. Hence, one desiring to increase the amount of his energy must give attention to all those conditions that improve the health. *Effect of Stimulants on the Energy Supply.*—In the effort to get out of the body as much as possible of work or of pleasure, various stimulants, such as alcohol, tobacco, and strong tea and coffee, have been used. Though these have the effect of giving a temporary feeling of strength and of enabling the individual in some instances to accomplish results which he could not otherwise have brought about, the general effect of their use is to lessen, rather than to increase, the sum total of bodily power. The student, for example, who drinks strong coffee in order to study late at night is able to command less energy on the day following. While enabling him to draw upon his reserve of nervous power for the time being, the coffee deprives him of sleep and needed rest. The danger of stimulants, so far as energy is concerned, is this: they tend to exhaust the bodily reserve so that there is not sufficient left for properly running the vital processes. Evidences of their weakening effect are found in the feeling of discomfort and lassitude which result when stimulants to which the body has become accustomed are withdrawn. Not until one gets back his bodily reserve is he able to work normally and effectively. Increase in bodily energy comes through health and not through the use of stimulants. *Summary.*—The body requires a continuous supply of energy. To obtain this supply, materials possessing potential, or stored-up, energy are introduced into it. The free oxygen of the air and the substances known as foods, on account of the chemical relations which they sustain to each other, contain potential energy and are utilized for supplying the body. So long as the foods are not oxidized, the energy remains in the potential form, but in the process of oxidation the potential energy is changed to kinetic energy and made to do the work of the body. *Exercises.*—1. In what different ways does the body use energy? 2. Show that a stone lying against the earth has no energy, while the same stone above the earth has energy.