CELLS 



and its place supplied by new food. So the object in tak- 

 ing food is both to supply the cells with what was burned 

 from them, and also to furnish fuel for the greater part of 

 the oxidation within the body. 



Water and mineral substances are not oxidized, but only 

 add weight to the cells of the body. Fat and starch give 

 only heat. Albumin gives both weight and heat, for it 

 both becomes a part of 

 the living cells and also 

 is oxidized. So anything 

 which gives either weight 

 or heat to the body is 

 food, 



13. Relation of plants 

 to animals. Man's food 

 comes both from animals 

 and from vegetables, but 

 animals feed upon vege- 

 tables, or else eat -other 

 animals which eat vege- 

 tables. Vegetables feed 

 upon substances in the 

 soil and air. The burned- Diagram of the restoration of oxygen to 

 up parts of man and ani- tne air after oxidation, and of the rebuild- 

 ing of burned material into living forms. 



mals go back to the soil 



and air and become food for plants. Thus plants build 

 the burned products of man's body into food, which can 

 be used once more by man. So year after year the 

 food makes the round from the soil to the plants, and then 

 to animals and man, and back again to the soil. A plant 

 lives on the soil a*nd air. An animal cannot live on these, 

 but must eat what plants have formed from them. This 

 makes the real difference between plants and animals. 



Carbonic Acid Gas 



in the air going 



into the tea/ 



