FOOD. 



53. The Source of All Food. 



The source of all of our food is the soil. Plants 

 grow in the soil and, while they take in carbon dioxide 

 through their leaves and nitrogen, after it has been 

 changed by the bacteria, through their roots, they could 

 not live if it were not for other material which is con- 

 tained in the soil. This material is chiefly potash and 

 phosphorus. Animals eat the plants and are used as part 

 of the food of man. 



Plant food and animal food are not very different 

 in regard to the kinds of material which they contain. 

 The difference comes in the proportions in which they 

 occur. We need our food for three reasons : to give us 



Cut supplied through United States Department of Agriculture, 



