VEGETABLE EXCRETIONS. 57 



imitate, and by which these materials are com- 

 bined into a variety of nutritive substances. Of 

 these substances, so prepared, one portion is con- 

 sumed by the plants themselves in maintaining 

 their own stmctures, and in developing the em- 

 bryos of those which are to replace them ; another 

 portion serves directly as food to various races of 

 animals ; and the remainder is either employed 

 in fertilizing the soil, and preparing it for subse- 

 quent and more extended vegetation, or else, 

 buried in the bosom of the earth, it forms part of 

 that vast magazine of combustible matter, des- 

 tined to benefit future communities of mankind, 

 when the arts of civilization shall have developed 

 the mighty energies of human power. 



Chapter III. 



ANIMAL NUTRITION IN GENERAL. 



^ 1 . Food of Animals. 



Nutrition constitutes no less important a part 

 of the animal, than of the vegetable economy. 

 Endowed with more energetic powers, and en- 

 joying a wider range of action, animals, com- 

 pared with plants, require a considerably larger 

 supply of nutritive materials for their sustenance, 



