18 BULLETIN 751, U. S. DEPARTMENT OF AGRICULTURE. 
The digestibility of the protein of white flour obtained by averag- 
ing the results of the 31 tests reported in the United States Depart- 
ment of Agriculture investigations noted on page 4 is found to be 88.1 
per cent. The digestibility of the protein of graham flour (repre- 
senting the whole kernel) obtained by averaging the results of the 
21 tests reported in the same investigations by the United States De- 
partment of Agriculture is found to be 76.9 per cent. If it is assumed 
that white flour contains 15.1 per cent 1 of protein which is 88.1 per 
cent digested and that fine bran contains 15.4 per cent 1 of protein 
which is 44.6 per cent digested, then by calculation the digestibility 
of the total protein supplied by a graham flour consisting of 72 per 
cent of white flour and the remainder of fine bran would be 75.8 per 
cent. It is an interesting coincidence that the value 75.8 per cent 
calculated for the digestibility of graham flour should agree so 
closely with the value 76.9 per cent obtained by averaging the results, 
of the determination of the digestibility of protein of graham flour 
found in the 26 digestion experiments noted above. 
The coefficients of digestibility of the diet as a whole (37 per 
cent for protein, 88.5 per cent for fat, and 79.8 per cent for carbo- 
hydrate, in the series in which fine bran was eaten, and 35.8 per 
cent for protein, 93.1 per cent for fat, and 82.8 per cent for carbo- 
hydrate, in the series in which coarse bran was eaten), are lower 
than the coefficients of digestibility, 92 per cent for protein, 95 per 
cent for fat, and 97 per cent for carbohydrate, reported 2 for the 
ordinary mixed diet. This indicates the way in which the rough, 
relatively indigestible bran influenced the digestibility of the entire 
diet. It is also possible that the bran stimulated peristaltic action to 
such an extent that the food materials were not as completely ab- 
sorbed as is normally the case when they pass through the alimentary 
tract without increased peristalsis. 
In general the amount of feces voided by the subjects during the 
tests with bran was larger than normal. This condition was noted 
by all the subjects regardless as to whether they were of active, ath- 
letic, or sedentary habits. Some of the subjects found the bran diets 
decidedly laxative. Little, if any, difference was noted by the sub- 
jects as a whole between the laxative effects of the fine and coarse 
brans. 
It is hoped that the results of the experiments here reported when 
considered in connection with the available data on the digestibility 
of wheat will be of value in determining the most economical and 
physiologically efficient method of utilizing wheat for human food. 
'U. S. Dept. Agr., Office Expt. Stas. Bui. 156 (1905), p. 14. 
2 Connecticut Storrs Sta. Rpt. 1901, p. 245. 
