18 SOURCE OF ANIMAL 



III. All living creatures, whose existence depends 

 on the absorption of oxygen, possess within them- 

 selves a source of heat independent of surrounding 

 objects. 



This truth applies to all animals, and extends, 

 besides, to the germination of seeds, to the flower- 

 ing of plants, and to the maturation of fruits. 



It is only in those parts of the body to which 

 arterial blood, and with it the oxygen absorbed in 

 respiration, is conveyed, that heat is produced. Hair, 

 wool, or feathers do not possess an elevated tempe- 

 rature. 



This high temperature of the animal body, or, as 

 it may be called, disengagement of heat, is uniformly 

 and under all circumstances the result of the combi- 

 nation of a combustible substance with oxygen. 



In whatever way carbon may combine with 

 oxygen, the act of combination cannot take place 

 without the disengagement of heat. It is a matter 

 of indifference whether the combination take place 

 rapidly or slowly, at a high or at a low tempera- 

 ture; 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 ex- 

 actly as much heat as if it had been directly burnt 

 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 intense ; in air it is slower, 



