60 THE CARBON OF THE BILE 



chief constituents of their bodies, and hence the 

 metamorphoses which their organs undergo must be 

 the same as those which, under the influence of the 

 vital force, take place in the matters which consti- 

 tute their food. 



The flesh and blood consumed as food yield their 

 carbon for the support of the respiratory process, 

 while its nitrogen appears as uric acid, ammonia, 

 or urea. But previously to these final changes, the 

 dead flesh and blood become living flesh and blood, 

 and it is, strictly speaking, the carbon of the com- 

 pounds formed in the metamorphoses of living tis- 

 sues that serves for the production of animal heat. 



The food of the carnivora is converted into blood, 

 which is destined for the reproduction of organised 

 tissues ; 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 shewn to take no share in the nutritive 

 process, serve to transport the oxygen, which they 

 give up in their passage 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 



