60 HUMAN BIOLOGY 



will devote considerable thought. This problem cannot 

 be solved, as we have seen, by consulting market prices 

 only, for often the highest-priced foods contain small per- 

 centages of the nutrients. Neither can we be sure of a good 

 supply of foods by following our tastes. To many people 

 cakes and sweetmeats are more appetizing than sandwiches 

 and cereals. Yet it is the latter that usually supply the 

 available proteins, at a lower cost. 



The composition of various foods can be found only by 

 chemical analysis, and their nutritive value can be deter- 

 mined only by experiment. Fortunately these analyses 

 and experiments are being carried on by the United States 

 government. The results are published in the Bulletins l 

 of the Department of Agriculture, Washington, D.C., many 

 of which will be sent free to any address. 



VII. DAILY DIET 



72. Amount of each nutrient required. Many in- 

 vestigations have been carried on, in this country and in 

 Europe, to determine the amount of each kind of nutrient 

 needed per day for the work of the body. The conclusions 

 that were drawn from this study are represented on the last 

 line of Fig. 22. According to these conclusions the average 

 American, when doing moderate work, requires about one 

 fourth of a pound, of proteins to provide for the growth and 

 repair of the body, and a quarter of a pound of fat and a 

 pound of carbohydrates to furnish the needed energy. 2 This 



1 The most suggestive of these publications are ** Foods, and 

 the Principles of Nutrition," "Meats: Composition and Cook- 

 ing"; "Milk as a Food"; "Fish as a Food"; "Sugar as a 

 Food." 



2 Recently, however, at the Scientific School of Yale University, 

 some very careful experiments have been performed by Professor 

 Chittenden which seem to prove that this quarter of a pound of pro- 



