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 equilibrium, 

 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, prehminary 

 and final periods were omitted. 



AH 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). 'U. S. Dept. Agr., Office Expt. Stas. Bui. 28 (1906). 



2 U. S. Dept. Agr., Bur. Chem. Bui. 107 (1912). 



