36 FOOD OF CAENIVORA AND HERBIVORA. 



At a mtiturer period of life, animals may be divided into two groups, 

 carnivorous and herbivorous, or those which feed exclusively on flesh, 

 and those which feed on vegetable substances. Between these may, 

 perhaps, be introduced a minor group, partaking of the manner of life of 

 both. 



The carnivorous animal finds in its prey all that is 'required for nutri- 

 Nutrition of tion ' anc * t ^ ie discharge f i ts functions. Digestion under these 

 carnivorous circumstances is reduced to its simplest conditions, and is 

 a s> scarcely more than a process of solution. In the stomach the 

 fibrin is brought into a soluble form ; in the duodenum the fats are re- 

 duced to an emulsion. The digestive apparatus has but little complexi- 

 ty. The stomach maybe regarded as a mere enlargement or pouch upon 

 the alimentary canal, having, along with the intestine, the office of bring- 

 ing the food into such a condition that it can be taken up by the veins 

 and lacteals, and so pass into the circulation. The various constituents 

 now revert into the same state in which they were before digestion be- 

 gan, the fibrin aiding in the repair of the wasted muscular tissues, and 

 the fats being deposited in the adipose cells. The bones, feathers, and 

 other such matters as have not been dissolved by digestion, are cast out. 



In the production of heat and motion the carnivorous animal consumes 

 itself, and, through the oxidation incessantly going on by means of the 

 air introduced by respiration, carbonic acid, ammonia, water, sulphuric 

 and phosphoric acids are constantly forming. 



On a superficial view it might be supposed that in the other group, 

 Nutrition of ^ e h^ivorous, * ne case * s quite different. These seem to 

 herbivorous spend all their lives in obtaining food. The ox or the horse, 

 put out into the pastures, is all the day long cropping the 

 grass. On a comparison of the quality and nature of the food which 

 they take with the substances of which their bodies consist, there seems 

 to be nothing in common. It was not, therefore, without reason that the 

 earlier physiologists imputed to the digestive organs of this class the 

 power of forming flesh and blood from vegetable matters. When, how- 

 ever, we come to a critical examination of the facts, we find that there is 

 no essential difference between them and the carnivora. 



When the expressed juice of vegetables is permitted to stand for a 

 time, though it may have been clear at first, a turbidity sets in, and a flaky 

 material is deposited. The substance thus possessing the power of spon- 

 taneous coagulation is identical in that property, and in composition, with 

 animal fibrin. After its deposit, if the clear liquid be warmed to near the 

 boiling point, it* again becomes turbid, and a second nitrogenized sub- 

 stance subsides, which, from its quality of coagulating by rise of tempera- 

 ture and its analysis, is inferred to be identical with animal albumen. 

 When this has been separated by filtration or otherwise, and the juice is 



