UNIFORM TEMPERATURE OF THE ANIMAL BODY. 19 



mass. It receives heat when the surrounding objects 

 are hotter, it loses heat when they are colder, than 

 itself. 



We know that the rapidity of cooling increases with 

 the difference between the temperature of the heated 

 body and that of the surrounding medium ; that is, the 

 colder the surrounding medium the shorter the time re- 

 quired for the cooling of the heated body. 



How unequal, then, must be the loss of heat in a 

 man at Palermo, where the external temperature is 

 nearly equal to that of the body, and in the polar re- 

 gions, 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 the in- 

 habitant of the arctic circle has a temperature as high as 

 that of a native of the south, who lives in so different a 

 medium. 



This fact, when its true significance is perceived, 

 proves that the heat given off to the surrounding medi- 

 um 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 by respiration, as has been 

 already shown, varies according to the temperature 

 of the external air ; the quantity of inspired oxygen in- 

 creases with the loss of heat by external cooling, and 

 the quantity of carbon or hydrogen necessary to com- 



