DIGESTIBILITY OF SOY-BEAN AND PEANUT FLOURS. re 
In order that the major portion of the protein supplied by the 
experimental diet should be derived from the soy-bean and peanut 
flours, the accessory foods were chosen to supply only a minimum of 
protein, and included oranges, butter, and tea or coffee with sugar if 
desired. Since the subjects ate very generous amounts of the bis- 
cuits but had a very limited diet in other respects it was thought that 
they would use large quantities of butter. It was found, however, 
that though they could have all they wanted they ate on an average 
only about 56 grams daily. 
DETAILS OF THE EXPERIMENTS. 
In this study of the digestibility of the proteins supplied by soy- 
bean and peanut flours the methods which were employed were very 
similar to those followed in the study of the grain sorghums.!| The 
usual 3-day or 9-meal experimental period was considered satis- 
factory for this study. No attempt was made to maintain a uniform 
body weight of the subjects or to maintain nitrogen equilibrium 
during the period. As is usual in such cases, sufficient food material 
was prepared at one time to supply all the subjects for the entire 
experimental period, representative samples of all the foods being 
retained for analysis. These samples and those of the air-dried 
feces of each subject resulting from the experimental diet were ana- 
lyzed in the usual way. The differences between the amounts of pro- 
tein, fat, and carbohydrates present in the foods and in the feces were 
taken to represent the amounts of these constituents digested. This 
method of procedure gives data regarding the digestibility of protein, 
fat; and carbohydrate supplied by the entire diet. Since in this 
study the coefficients of digestibility of the soy-bean and peanut pro- 
teins are of special interest they have been estimated by making 
allowance for the undigested protein material occurring in the fen 
~The method followed in estimating the digestibility of the proteins 
_supplied by the soy beans and peanuts is indicated by the following 
~ equations: 
[Weight of protein in accessory food are x [Percentage of 
undigested protein in each]=[Protein in feces from food other than 
- bread]. : 
_ [Total protein in feces]—[Protein in feces from food other than 
bread]=[Weight of undigested bread protein. | 
[Weight of protein in bread]—[Weight of undigested bread pro- 
tein]+[Weight of protein in bread] =[Estimated percentage of avail- 
ability of bread protein.] 
In determining the amount of undigested protein present in the 
accessory food materials in the experimental diet it was assumed that 
1U.S. Dept. Agr. Bul. 470 (1916), pp. 30. 
