HEAT. RESPIRATION. 19 



the temperature is not so high, but it continues 

 longer. 



It is obvious that the amount of heat liberated 

 must increase or diminish with the quantity of 

 oxygen introduced in equal times by respiration. 

 Those animals which respire frequently, and conse- 

 quently consume much oxygen, possess a higher 

 temperature than others, which, with a body of 

 equal size to be heated, take into the system less 

 oxygen. The temperature of a child (102) is 

 higher than that of an adult (99-5). That of birds 

 (104 to 105-4) is higher than that of quadrupeds 

 (98-5 to 100-4) or than that of fishes or amphibia, 

 whose proper temperature is from 2*7 to 3*6 higher 

 than that of the medium in which they live. All 

 animals, strictly speaking, are warm-blooded ; but 

 in those only which possess lungs is the temperature 

 of the body quite independent of the surrounding 

 medium. (5) 



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 in what are commonly called warm- 

 blooded animals, is invariably the same ; yet how dif- 

 ferent are the circumstances under which they live ! 



The animal body is a heated mass, which bears the 

 same relation to surrounding objects as any other 

 heated mass. It receives heat when the surround- 

 ing objects are hotter, it loses heat when they are 

 colder than itself. 



c 2 



