The Manufacture of Food 



45 



food. However, recent experiments in animal feeding have 

 shown that for maintenance and growth some proteins are more 



Soy beans 



7-5 '2.7 9.7 78 6.8 



Fig. 26. Percentage of protein in various foods. 



valuable pound for pound than others. Curiously enough, the 

 protein of the soy bean is not only furnished in large amounts, 

 but in its abihty to be digested and assimilated it stands at the 

 very top of the vegetable proteins. It is of interest to know that 

 even in the United States, where meat is consumed in compar- 

 atively large quantities, the principal source of protein in our 

 diet is wheat. 



Importance of understanding the food-making processes. A 

 knowledge of the essential facts of food manufacture by plants 

 Hes at the foundation of all agricultural, horticultural, and silvi- 

 cultural practices. 



We have gone far enough now to be perfectly sure that plants 

 do not get their food from the soil any more than animals do. Both 

 plants and animals require varit)us salts. Plants get these salts 

 from the soil, but they constitute only from i to 3 per cent of the 

 plant body. Both plants and animals require carbohydrates , fats , 

 and proteins as their principal food. Animals can obtain these 

 from plants, but green plants must manufacture them. 



