CASEINE IDENTICAL. 53 



production of blood, because the iiitrogenised sub- 

 stances contained in the food already contain exactly 

 the amount of carbon which is required for the pro- 

 duction of fibrine and albumen. 



The following considerations will shew that hardly 

 a doubt can be entertained, that this excess of car- 

 bon alone, or of carbon and hydrogen, is expended 

 in the production of animal heat, and serves to pro- 

 tect the organism from the action of the atmospheric 

 oxygen. 



XI. In order to obtain a clearer insight into the 

 nature 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 retained 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, namely, the gelatine. Faeces, properly 

 so called, do not occur in serpents any more than in 

 carnivorous birds. 



We find, moreover, that, when the serpent has 

 regained its original weight, every other part of its 

 prey, the flesh, the blood, the brain, and nerves, in 

 short, every thing, has disappeared. 



