ANATOMY AND PHYSIOLOGY 



cumstances the result of the combination of com- 

 bustible substance with oxygen. 



" In whatever way carbon may combine with oxy- 

 gen, the act of combination cannot take place without 

 the disengagement of heat. It is a matter of indiffer- 

 ence whether the combination takes place rapidly or 

 slowly, at a high or at a low temperature ; the amount 

 of heat liberated is a constant quantity. The carbon 

 of the food, which is converted into carbonic acid 

 within the body, must give out exactly as much heat 

 as if it had been directly burned in the air or in oxygen 

 gas; the only difference is that the amount of heat 

 produced is diffused over unequal times. In oxygen 

 the combustion is more rapid and the heat more in- 

 tense ; in air it is slower, 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 amount of oxygen 

 introduced in equal times by respiration. Those ani- 

 mals which respire frequently, and consequently con- 

 sume 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 tnan that of fishes or 

 amphibia, whose proper temperature is from 3.7 to 

 2.6 higher than that of the medium in which they 

 live. All animals, strictly speaking, are warm-blood- 

 ed ; but in those only which possess lungs is the tem- 

 perature of the body independent of the surrounding 

 medium. 



133 



