BREATHING 179 



242. How the Bodily Heat is produced. The heat of the 

 body is produced in just as simple a manner as that which 

 comes from a common fire or a lighted candle. It is the 

 natural result of the process of combustion. Our bodies 

 are warm because we are burning away bit by bit, just as 

 a candle does, that is to say, by the union of carbon, or 

 charcoal, with oxygen. There is only this difference : we 

 burn wet materials (the moist tissues), and do not give out 

 flame or light. In place of coal or tallow we take in fuel 

 in the shape of starch, sugar, and fat and get the oxygen 

 from the air we breathe. 



A steam engine at work is warm because all the energy 

 set free from the fuel burned is not turned into mechanical 

 work, but some of it appears as heat. So it is in our bodies. 

 Every tiny cell of every bit of tissue is busily at work, and 

 its substance is slowly being burned at a low temperature. 

 Every time we move, feel, or think, this oxidation, or burn- 

 ing, goes on in all the tissues of the body. 



Some of the energy thus set free by this slow combus- 

 tion shows itself as heat, which helps to keep the body 

 warm and at its natural temperature. Thus, animal heat 

 is produced and life maintained. 



Experiment 56. To show the natural temperature of the body. 

 Borrow a physician's clinical thermometer and take your own tem- 

 perature, and that of several friends, by placing the instrument under 

 the tongue and holding it there for five minutes, keeping the mouth 

 closed. Read it while in position, or the instant the instrument is 

 removed. The natural temperature is about 98^ F. The ther- 

 mometer should be thoroughly cleansed after each use. 



243. How the Body loses its Heat. Our bodies are 

 warmer than the surrounding air, except in the hottest 

 weather ; hence there must be a loss of heat nearly all 



