WHAT TO EAT 



body in health. Day and night, summer and winter, 

 the organism scarcely varies by so much as a single 

 degree centigrade from the same normal level. The 

 interior of the body is indeed warmer than the surface, 

 but the swiftly flowing blood tends naturally to establish 

 equilibrium. Even under stress of the maladjustment 

 due to disease, the range of temperature is only a few 

 degrees, rarely more than six. 



This of course implies the existence of bodily mechan- 

 isms for regulating of the elimination of heat. The 

 skin, with its perspiratory apparatus, is the most con- 

 spicuous of these. When the pores are open and per- 

 spiration is active, the evaporating liquid exerts an 

 enormous cooling influence. On the other hand, when 

 the pores are closed and the excretions reduced to a 

 minimum, the skin serves as a relatively impervious 

 barrier, and the bodily heat is conserved to a remarkable 

 degree. Yet at the very best there is a considerable 

 loss of heat, and the body would quickly cool below the 

 life-line were the combustion-fires to be quite extin- 

 guished. 



Such physiological explanations as this serve, after 

 all, only to give technical expression to the familiar 

 knowledge that the body must be perpetually supplied 

 with food. It required no scientific analysis to teach 

 mankind that elementary truth. Yet it is always of 

 interest to know the whys of the most familiar phenom- 

 ena, and, moreover, it is always possible that the ex- 

 planation of an old truth may put us in line of dis- 

 covery of facts that arc not so familiar. 



In the present instance, for example, we shall be 



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