GROWTH OF ANIMALS; ANIMAL FOOD 137 



CHAPTER XII. 



The Growth of Animals ; The Constituents of Animals and Ani- 

 mal Food ; The Character and Composition of Fodders and Feeds. 



In our study of the growth of plants, it was shown 

 that, with the exception of the food stored in the seed, 

 the plant was built up of single chemical elements, and 

 that these were derived from sources outside of itself, 

 viz., the atmosphere and soil, and formed by the living 

 plant into organized plant substances. The growing of a 

 plant, therefore, is a constructive process ; elements that 

 exist separately are gathered from different sources, and 

 combined and fixed in special forms. 



The growth of the animal is more complicated. It is 

 built up and nourished by the consumption of substances 

 ready formed in plants, or which .have been derived from 

 them. It is a double process, — first, a disorganizing, or 

 tearing apart of these substances formed in the plant; 

 and second, a building or forming process in which they 

 are brought together again, and fixed in the form of 

 flesh and bone. 



Composition of the Animal Body. — The animal 

 body, therefore, is composed of substances or elements 

 common to the plants from which it was directly or in- 

 directly derived. It may be divided, first, into two 

 classes of products, water and dry substance. 



