THE NECESSITY OF FOOD. 97 



by the oxidation appears as heat, assisting to keep the 

 body warm, and at its best working temperature. 



A second reason why we need food. Since the body only 

 works well at a temperature which is higher than that of 

 the air around it (except on a very hot day), and in health 

 always keeps at this temperature, it must lose heat nearly 

 all the time: At night each of us is, in health, just as warm 

 as in the morning ; and in the morning as when we went 

 to bed ; though we have lost heat to the air during the 

 day, and to the bedclothes at night. In order to keep our 

 bodies at the temperature most suitable to their activity, 

 they must, therefore, generate heat all the time, to com- 

 pensate for the giving of it from them to the outer world. 

 In this necessity of generating heat we find a second reason 

 for the need of food : we require daily to take into our- 

 selves things which can be burned (or oxidized) in the 

 body, and which in so doing will give off heat. 



The influence of starvation upon muscular work and 

 animal heat. When a man is deprived of food the supply 

 of things which can be oxidized in his body is cutoff. The 

 tissues and organs are used up and not renewed ; his tem- 

 perature falls, his muscles become weaker and weaker, and 

 at last he dies. The body does not live, and work, and 

 keep warm, by means of a peculiar vital force or energy 

 which inhabits it, but by utilizing the energy set free in it 

 by the oxidation of foods, or of things made in it from 

 foods. If the food supply be cut off, the body first uses up 



What must we conclude from the fact that our bodies keep at 

 nearly the same temperature all the time? How do we know that 

 they generate heat? Give a reason for taking food, in addition to ita 

 use as a source of energy to be spent by the muscles. 



What happens when a man is starving ? How does the body live, 

 and keep warm, and work? What first happens when the food sup- 

 ply is stopped? 



