124 ANIMAL FUNCTIONS. 



properties there is an essential difference in the articles 

 usually employed in diet. Some substances which con- 

 tain the elements of chyle in abundance afford little 

 nutriment because they do not readily go through the 

 digestive process ; while others which contain compara- 

 tively but a small quantity of these elements, afford 

 more nourishment, because they are more completely 

 dissolved by the gastric juice. Animals in the natural 

 state adhere with remarkable uniformity to the same 

 kinds of food. There are many carnivorous animals 

 which feed only on a certain kind of flesh ; some upon 

 the flesh of quadrupeds ; others upon that of birds ; and 

 others again upon that of insects. Among herbivorous 

 animals, some subsist only on certain kinds of plants ; 

 others on certain parts of particular plants, as the seed, 

 the fruit, the leaves, and so on, while entire tribes of 

 insects appear to be exclusively attached to some one 

 species of vegetable matter. 



We have seen that there is a manifest connection 

 between the substances on which animals feed and the 

 structure of their masticating organs, indicating that the 

 selection is not the effect of accident, but depends on 

 the original conformation of the parts. Thus, as we 

 have already shown, the teeth of some are constructed 

 for seizing and tearing ; others for gnawing, arid others 

 only for cropping the delicate parts of plants. The 

 beaks and claws of carnivorous birds, are most formid- 

 able weapons ; while those of the goose and duck are 

 formed only for scooping and swimming. All these 

 diversities of structure are obviously adapted to receive 

 as great a variety of food. We have seen also, that the 

 stomachs of animals are of different forms and capaci- 

 ties, and that there is an intimate relation between 

 their masticating organs and the powers of digestion. 



Man requires a variety of Food. The structure of 

 our own species as already shown, places man between 

 the carnivorous and herbivorous animals with respect 



Why do not substances containing equal portions of the elements of 

 chyle afford equal nourishment 1 What is said of the adherence of ani- 

 mals to the same kind of food'? Where is man placed in the scale of 

 creation with respect to his food-'? 



