The Manufacture of Food 



33 



ported from the leaves by the food-conducting tissue of the 

 bundles. 



Soy beans 



28.3 



17.5 12.7 9.7 78 6.8 



Fig. 20. Percentage of protein in various foods. 



The most expensive portion of the diet of human beings is 

 the proteins. Figure 20 shows that in soy beans we possess 

 the richest source of protein. It also shows why the soy 

 bean is one of the most important of foods in the Asiatic 

 nations, where animal foods are very limited. One dollar 

 wiU buy several times as much protein in soy beans as it 

 win in any other plant or animal food. However, recent ex- 

 periments in animal feeding have shown that for mainte- 

 nance and growth some proteins are more valuable pound 

 for pound than others. 



Amount of food produced per acre. Since the food supply 

 of aU living beings depends primarily upon these synthetic 

 processes that are carried on in plants, it is of interest to 

 inquire how much food may be derived from an average acre 

 of land when planted to different crops. It must be remem- 



