10 THE FEEDING OF ANIMALS 



2. The plant stores energy.— Plant life both synthesizes 

 simpler compounds into complex organic substance and 

 stores energy. We get evidence of this fact when wood 

 is utilized as fuel for the production of heat, heat being 

 one form of energy. Scientific investigation has traced 

 the source of this heat to the chemical energy of the sun's 

 rays, which becomes stored in the plant. Combustion 

 of the plant tissue liberates this energy in another forni. 

 Not only does this energy become available as heat, but 

 it is also available for a variety of uses in the animal 

 body. (See Pars. 206, 207.) 



3. Plant substance a source of animal substance. — 

 The animal body, outside of the water which it con- 

 tains, has its immediate origin in the food which the 

 animal consumes. The mass of bone and fle^ which 

 make up the body of the immense bullock is derived from 

 the plant substance which, in other combinations, was 

 collected from the soil and air. The animal eats his 

 daily ration and makes his daily gain of tissue. If food 

 is withdrawn, his body wastes and dies. If his food varies 

 in amount, his growth is somewhat proportional to the 

 quantity eaten. It is self-evident that the bones, blood, 

 and flesh of an animal are derived from what he eats. 



4. The plant a source of animal heat. — ^The plant not 

 only supplies building-material for the animal body, but 

 is the soiu-ce of the heat with which the animal organ- 

 ism is kept warm. No matter how cold the surrounding 

 atmosphere, we find that when in health the temperature 

 of the ox remains at about 101° F., with but small varia- 

 tion. Just as we warm a room through the combustion 

 of vegetable matter, such as wood, so the temperature 

 of the animal is kept at the necessary heat by tiie com- 

 bustion of his food. The combustion, in the latter case. 



