12 BULLETIN 717, U. S. DEPARTMENT OF AGRICULTURE. 
Osborne and Mendel‘ also report that they have been able to 
demonstrate the presence of the water-soluble food accessory in 
peanut meal. 
In summarizing the studies of the nature and value of soy-bean 
and peanut proteins, referred to above, it appears first that chemical 
analysis of glycinin and arachin shows them to be relatively rich in 
lysine and tryptophane, amino acids essential for growth and main- 
tenance, and second that studies of their biologic value show them to 
be more efficient proteins than those supplied by the common cereals 
or many of the common legumes. It appears then from these facts 
that soy-bean and peanut proteins have a high nutritive value and 
that further studies of their value in the human dietary are to be 
desired. 
THE DIGESTIBILITY OF SOY-BEAN AND PEANUT PROTEINS. 
This investigation was undertaken for the purpose of determining 
the digestibility of these proteins by normal individuals when eaten 
as a constituent of a simple mixed diet. It is of course recognized 
that the oil remaining in the soy-bean and peanut flours contributes 
to the food value of these flours, but no special attention is given to 
these oils in this study since previous studies of peanut ? and soy-bean 
oils ? have shown that both are very well utilized by the human body. 
PREPARATION OF SOY-BEAN AND PEANUT PRESS-CAKE FLOURS. * 
The soy-bean flour used in the experiments which follow was pre- 
pared by expelling the oil from 2 bushels of well-cleaned Mammoth 
Yellow soy beans which had been grown under controlled experi- 
mental conditions by Forage Crop Investigations of the Bureau of 
Plant Industry. In order to secure a more nearly complete removal 
of the oil than is usual, the cake was pressed a second time. The 
press cake thus obtained was of a yellow color and retained about 8 
per cent of oil. It was ground in a small-sized burr mill until all of 
the meal passed through a millimeter sieve. Through the courtesy 
of H. 8. Bailey, of the Bureau of Chemistry, it was possible to pre- 
pare both the soy-bean and peanut flours under conditions approxi- 
mating those of the commercial oil mill, using for this purpose a 
continuous process expeller type of oil-expressing machine. 
In order to secure data relative to the fineness of this flour, a sam- 
ple was bolted, and it was found that 53 per cent of the flour re- 
mained on the 40-mesh sieve, 23 per cent remained on the 70-mesh 
sieve, 9 per cent remained on the 90-mesh sieve, 3 per cent remained 
1 Jour. Biol. Chem., 32 (1917), No. 3, p. 310. 
2U.S. Dept. Agr. Bul. 505 (1917), p. 18. 
3U.S. Dept. Agr. Bul., 687 (1918), p. 6. 
4In this paper the term ‘‘flour’”’ is used without reference to the coarseness of the ground soy-bean 
and peanut press cakes. 
