18 
BULLETIN 310, U. S. DEPARTMENT OF AGRICULTURE. 
which are ordinarily designated as metabohc products. These 
include residues of bacteria, digestive juices, internal secretions, and 
epithelial cells of the stomach and intestines. Some of these products 
of the body metabolism are soluble in ether and therefore occur in the 
ether extract of the feces, together with the fat actually unavailable. 
Moreover, these metabolic products are not derived necessarily from 
the fat under consideration, but may be formed from protein and 
carbohydrate as well, and probably are produced partly from food 
eaten prior to the beginning of the experimental period. 
To determine either the amount or the percentage of fat actually 
unutilized as distinguished from the total fecal fat (often called " un- 
digested fat")? allowance must be made for fat in the fecal metabolic 
products. The method adopted is not a direct one, since it is imprac- 
tical to make the separation quantitatively, but is based on the 
assumption that the quantity and quality of metabolic products 
found depend on the nature and the amount of ingested food — that 
the average percentage of metabohc products found in the ether 
extract when the basal ration alone is eaten will be approximately 
equal to that when the basal ration together with added fat is con- 
sumed. 
Four experiments are herein reported with the basal ration with- 
out added fat. The procedure was in no way different from that 
employed in those tests in which large amounts of added fat were 
eaten, the bulk of food in each series of experiments being approxi- 
mately equal. The results of these tests are given below and 
furnish a basis for calculating the necessary allowance for the meta- 
bohc products contained in the ether extract of the feces. 
Data of digestion experiments with basal ration. 
Weight. 
Water. 
Protein. 
Fat. 
Carbo- 
hydrates. 
Ash. 
Experiment No. 266, subject H. F. B.: 
Blanc mange without added fat 
Grams. 
2,307.0 
592. 
1,392.0 
208.0 
Grams. 
1,296.8 
47.4 
1,211.0 
Grams. 
45.4 
65.1 
13.9 
Grams. 
14.5 
17.8 
Grams. 
939.0 
449.9 
167.1 
208.0 
Grams. 
11.3 
11.8 
Fruit 
4,499.0 
136.0 
2, 555. 2 
124.4 
38.9 
85.5 
32.3 
11.8 
20.5 
1,764.0 
73.4 
1,690.6 
23.1 
11.9 
11.2 
68.7 
63.5 
95.8 
48.5 
Experiment No. 267, subject D. G. G.: 
Blanc mange without added fat 
1,922.0 
335.0 
1,027.0 
149.0 
1,080.4 
26.8 
893.5 
37.9 
36.9 
10.3 
12.1 
10.0 
782.2 
254.6 
123.2 
149.0 
9.4 
6.7 
Fruit 
3,433.0 
87.0 
2,000.7 
85.1 
28.6 
56.5 
22.1 
8.3 
13.8 
1,309.0 
42.2 
1,266.8 
16.1 
7.9 
8.2 
Per cent utilized 
66.4 
62.4 
96.8 
50.9 
