204 A HA Y INFUSION. 



A hay infusion thus affords in miniature a picture of the liv- 

 ing world. The green plants are constructive, and in the sun- 

 light build up matters rich in potential energy. These as foods 

 support colorless plants (such as bacteria) or animals. On these, 

 again, herbivorous and carnivorous animals feed ; and so, in the 

 world at large, as in the hay infusion, omnivorous as well as 

 carnivorous animals, in the long run, feed upon herbivorous 

 animals, and the latter upon plants either colorless or green 

 which thus stand as the bulwark between animals and starvation. 



