UNDERGOES COMBUSTION. 59 



strictly speaking, the carbon of the compounds formed 

 in the metamorphoses of living tissues that serves for 

 the production of animal heat. 



The food of the carnivora is converted into blood, 

 which is destined for the reproduction of organized tis- 

 sues ; and by means of the circulation a current of 

 oxygen is conveyed to every part of the body. The 

 globules of the blood, which in themselves can be 

 shown to take no share in the nutritive process, serve to 

 transport the oxygen, which they give up in their pas- 

 sage through the capillary vessels. Here the current of 

 oxygen meets with the compounds produced by the 

 transformation of the tissues, and combines with their 

 carbon to form carbonic acid, with their hydrogen to 

 form water. Every portion of these substances which 

 escapes this process of oxidation is sent back into the 

 circulation in the form of the bile, which by degrees 

 completely disappears. 



In the carnivora the bile contains the carbon of the 

 metamorphosed tissues ; this carbon disappears in the 

 animal body, and the bile likewise disappears in the vital 

 process. Its carbon and hydrogen are given out through 

 the skin and lungs as carbonic acid and water ; and 

 hence it is obvious, that the elements of the bile serve 

 for respiration and for the production of animal heat. 

 Every part of the food of carnivorous animals is capable 

 of forming blood ; their excrements, excluding the 

 urine, contain only inorganic substances, such as phos- 

 phate of lime ; and the small quantity of organic matter 

 which is found mixed with these is derived from excre- 



