14 BULLETIN 717, U. S. DEPARTMENT OF AGRICULTURE. 
THE SUBJECTS OF THE DIGESTION EXPERIMENTS. 
Seven subjects with previous experience in experiments which 
were made to determine the digestibility of some edible fats assisted 
in this investigation. In general they were students of dental or 
medical schools and were of normal health and appetite. Their. 
ages ranged from 20 to 40 years and their activities were such that 
they would be classified as moderately-active persons. As is always 
the case, they were instructed to exercise care in saving all uneaten 
portions of the food, in separating and collecting the feces, and in 
submitting reports concerning their physical condition before, after, 
and during the experimental period. Inasmuch as all seemed in 
their usual good physical condition throughout the entire time of 
the experiments, no detailed discussion of these reports is given. 
- PREPARATION OF EXPERIMENTAL DIETS. 
As in all studies of this character, it was desired that the nutrient — 
under consideration, in this case the proteins supplied by soy-bean 
and peanut flours, should comprise as large a portion as possible of 
the total protein of the diet. It is essential that the foods studied 
be prepared in an acceptable form and accordingly preliminary tests 
were made of a number of methods of preparing these flours for 
eating. As a result of these tests it appeared that ‘‘tea biscuits”’ 
similar to those so commonly made with wheat flour were well adapted 
to this purpose. The recipe used follows: y 
RECIPE FOR BISCUITS. - 
16 cups flour mixture. 12 teaspoons salt. 
16 tablespoons lard. 10 tablespoons baking powder. 
6 cups water. 
In the soy-bean experiments the flour mixture was prepared by 
mixing equal portions of wheat flour and soy-bean flour. In the 
experiments with the peanut flour made from roasted kernels, the 
proportion was two-thirds wheat flour and one-third peanut flour, 
and in the experiments with peanut flour made from the raw kernels 
from which the red skin was not removed, the proportion was one to 
one. The wheat flour used in all cases was a commercial brand of 
patent flour. 
Biscuits made with flour and soy-bean flour or peanut flour one to 
one were satisfactory when only one-half or three-fourths inch in 
thickness; thicker biscuits being very often rather ‘‘heavy,” no doubt 
because the amount of gluten in the flour mixture was rather small. 
It was found that if the biscuits were very thoroughly baked (though 
not scorched) they possessed a much better flavor than those not so 
well done. 
