A HISTORY OF SCIENCE 



"The most trustworthy observations prove that in 

 all climates, in the temperate zones as well as at the 

 equator or the poles, the temperature of the body in 

 man, and of what are commonly called warm-blooded 

 animals, is invariably the same ; yet how different are 

 the circumstances in which they live. 



" The animal body is a heated mass, which bears the 

 same relation to surrounding objects as any other heat- 

 ed mass. It receives heat when the surrounding ob- 

 jects are hotter, it loses heat when they are colder 

 than itself. We know that the rapidity of cooling 

 increases with the difference between the heated body 

 and that of the surrounding medium that is, the 

 colder the surrounding medium the shorter the time 

 required for the cooling of the heated body. How 

 unequal, then, must be the loss of heat of a man at 

 Palermo, where the actual temperature is nearly equal 

 to that of the body, and in the polar regions, where 

 the external temperature is from 70 to 90 lower. 



"Yet notwithstanding this extremely unequal loss 

 of heat, experience has shown that the blood of an in- 

 habitant of the arctic circle has a temperature as high 

 as that of the native of the South, who lives in so dif- 

 ferent a medium. This fact, when its true significance 

 is perceived, proves that the heat given off to the sur- 

 rounding medium is restored within the body with 

 great rapidity. This compensation takes place more 

 rapidly in winter than in summer, at the pole than at 

 the equator. 



" Now in different climates the quantity of oxygen 

 introduced into the system of respiration, as has been 

 already shown, varies according to the temperature of 



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