16 BULLETIN 717, U. S. DEPARTMENT OF AGRICULTURE. 
the protein! of wheat flour was 93.8 per cent digested, the protein? of 
orange 85 per cent, and the protein? of butter was 97 per cent 
digested. | 
It is, of course, recognized that the calculated values so obtained, 
for a special food, in this case soy-bean and peanut proteins, are 
probably somewhat low, since they include the errors due to consider- 
ing all fecal nitrogen not resulting from the accessory foods as undi- 
gested soy-bean or peanut nitrogen, whereas fecal nitrogen, as has 
been pointed out by Woods and Merrill,? Crowther and Woodman,* 
and others, is derived in part at least from bile residues, epithelial 
waste, stomach residues, mucus, and saliva. It is not believed, 
however, that in this instance the error occasioned by the inability to 
correct for this factor is significant, especially in view of the unusually 
large quantities of soy-bean or peanut proteins consumed. 
THE DIGESTIBILITY OF PROTEIN SUPPLIED BY SOY-BEAN PRESS- 
CAKE FLOUR. 
In spite of the very extensive use of soy beans by the oriental 
peoples there appears to be little experimental data reported regard- 
ing the digestibility of the proteins supplied by this protein-rich 
legume. However, the long use of the soy bean as a staple article 
of the diet by the Japanese and Chinese offers sufficient evidence that 
soy-bean protein is well tolerated by the human body. Oshima in a 
summary of Japanese nutrition investigations, which includes much 
interesting information regarding the digestibility of preparations of 
legumes in common use in Japan, reports three experiments * in which 
the subjects ate approximately 200 grams of tofu (soy-bean curd) 
daily in conjunction with cooked rice, The average digestibility of 
the total protein supplied by these diets, of which 83 per cent was 
soy-bean protein, was 95 per cent, | | 
Few studies of the digestibility of soy-bean protein have been made 
in this country, Mendel and Fine report ® an experiment of six days’ 
duration in which soy beans supplied 90.5 per cent of the total 
nitrogen intake, the basal ration consisting of tomatoes, apples, 
oranges, milk, sugar, and butter. Thesoy beans were boiled in water 
for one-half hour and the tomatoes thoroughly incorporated with the 
resulting mush which had been salted to taste. The total nitrogen 
supplied by the diet was 85.3 per cent digested. The subject re- 
ported that he was in excellent condition throughout the whole 
experiment. Defecation was regular and no physiological disturb- 
ances were experienced. The same authors conducted two series of 
1U.S. Dept. Agr., Office Expt. Stas. Bul. 143 (1904), p. 32. 
2 Connecticut Storr’s Sta. Rpt. 1899, p. 104. 
3U.S. Dept. Agr., Office Expt. Stas. Bul. 143 (1904), p. 57. 
4 Jour. Agr. Sci., 8 (1917), pp. 429-477, Part IV. 
6U.S. Dept. Agr., Office Expt. Stas. Bul. 159 (1905), pp. 224. 
6 Jour. Biol. Chem., 10 (1911), pp. 433=458. 
