6 BULLETIN 470, U. S. DEPARTMENT OF AGRICULTURE. 
SUBJECTS OF THE EXPERIMENTS. 
The seven subjects who assisted in the digestion experiments had 
acquired experience in work of this kind from the tests conducted in 
the Office of Home Economics with animal fats. 1 They were young 
men of medium weight and of good health, capable of following 
instructions carefully, and well informed as to the details and condi- 
tions of the experiments. As usual in work of this kind, they were 
informed that regularity in all of their daily habits was highly desir- 
able. No prescribed hour for eating or regular exercise other than 
that ordinarily obtained in pursuance of their daily routine was 
required. 
METHODS OF PROCEDURE. 
The methods employed closely resembled those tested and found 
satisfactory in the experiments with the fats. In order to obtain a 
uniform product the ingredients of the breads and mushes were thor- 
oughly mixed, and care was taken to maintain a constant temperature 
during the cooking process. In each instance sufficient material was 
prepared at one time to supply all the subjects for the entire test 
period. The quantity of the bread or mush eaten was not restricted 
nor were any of the other components of the diet limited except the 
potato. In the diets of which the latter formed a part it was given 
in restricted quantities, so that the potato protein should not form 
too large a proportion of the total protein content of the diet. 
No attention was paid to the maintenance of nitrogen equihbrium, 
nor were collections and analyses of the urine made to determine 
what percentage of energy, owing to the occurrence of incompletely 
oxidized nitrogen in the urine, was not available. Factors based on 
the results of earlier work were used to estimate indirectly the amount 
of energy actually available to the body. A record of body weights 
was not kept, for the purpose of the investigation was primarily the 
determination of the coefficients of digestibility of the grain sor- 
ghums. The 3-day or 9-meal period was judged to be of sufficient 
duration to permit of accurate analytical results, and since the ration 
was made up to resemble closely the ordinary mixed diet, preliminary 
and final periods were omitted. 
All analyses were made according to the methods outlined by 
the Association of Official Agricultural Chemists. 2 Separation of the 
feces of a test period was accomplished by the use of charcoal taken 
in gelatin capsules with the first meal of the experiment and with the 
first meal succeeding the 3-day period. Samples of the bread and of 
the air-dried feces were analyzed, but the composition of the potato, 
apple sauce, and butter was estimated by comparison with the average 
values of a large number of earlier analyses. 3 Allowances were made 
i U. S. Dept. Agr. Bui. 310 (1915). 3U. S. Dept. Agr., Office Expt. Stas. Bui. 28 (1906). 
- U. S. Dept. Agr., Bur. Chem. Bui. 107 (1912). 
