ENERGY SUPPLY OF THE BODY 195 



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 stimu- 

 lants, 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 weak- 

 ening 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 withdrawn.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 oxi- 

 dized, 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. i. 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. 



