CHAPTER IX. 



THE DYNAMICS OF LIFE. 



Vegetables 

 form or- 

 ganic com- 

 pounds, 

 whicli are 

 oxidised 

 by ani- 

 mals. 



Their ac- 

 tions are 

 opposite. 



Animal 

 assimila- 

 tion. 



TTTE have seen in the last chapter that vegetables form 

 ' ' the characteristically organic compounds ; these 

 serve as the food of animals, and, after undergoing an assi- 

 milative change in their nutritive systems, become part of 

 their tissues. The organic compoiinds afterwards undergo a 

 change, chiefly consisting in oxidation, which totally alters 

 their chemical character, and makes them incapable of any 

 longer forming part of a living tissue, so that they are cast 

 out as waste materials. 



Animals feed on vegetables, and vegetables feed on 

 inorganic matter. That is to say, vegetables derive the 

 carbon, hydrogen, nitrogen, and oxygen, which are found 

 variously combined in their substance, from the carbonic 

 acid, water, and ammonia of the atmosphere. The 

 assimilation to which an animal subjects its vegetable 

 food before that food can become part of its tissues, 

 though of course it is an all-important process for 

 the purposes of life, effects but a very slight chemical 

 change, and an exactly similar assimilative process is 

 necessary when the food consists of the flesh of other 

 animals. 



So that we may broadly say, that vegetables form the 

 organic compounds out of the materials of the inor- 

 ganic world, and animals give them back to the inorganic 

 world again, in the form of waste material. Thus the 

 relations of vegetables and of animals to matter are 

 opposite. 



