52 ANIMAL AND VEGETABLE 



There is added, therefore, by means of these com- 

 pounds, to the nitrogenized constituents of food, a cer- 

 tain amount of carbon, or, as in the case of butter, of 

 carbon and hydrogen ; that is, an excess of elements, 

 which cannot possibly be employed in the production 

 of blood, because the nitrogenized substances contained 

 in the food already contain exactly the amount of car- 

 bon which is required for the production of fibrine and 

 albumen. 



The following considerations will show that hardly a 

 doubt can be entertained, that this excess of carbon 

 alone, or of carbon and hydrogen, is expended in the 

 production of animal heat, and serves to protect the 

 organism from the action of the atmospheric oxygen. 



XI. In order to obtain a clearer insight into the na- 

 ture of the nutritive process in both the great classes of 

 animals, let us first consider the changes which the food 

 of the carnivora undergoes in their organism. 



If we give to an adult serpent, or boa constrictor, a 

 goat, a rabbit, or a bird, we find that the hair, hoofs, 

 horns, feathers, or bones of these animals, are expelled 

 from the body apparently unchanged. They have re- 

 tained their natural form and aspect, but have become 

 brittle, because of all their component parts they have 

 lost only that one which was capable of solution, name- 

 ly, the gelatine. Fsces, properly so called, do not 

 occur in serpents any more than in carnivorous birds. 



We find, moreover, that, when the serpent has re- 

 gained its original weight, every other part of its prey, 



