10 
BULLETIN 649, U. S. DEPARTMENT OE AGRICULTURE. 
Denis 1 in a study of the blood of a number of fishes found urea in 
the blood of the grayfish. An analysis of the canned grayfish showed 
that the flesh of this fish contained both ammoniacal and urea 
nitrogen. The amount of nitrogen present in this form is, however, 
relatively small, and when allowance was made in the experiments 
which follow for this nonprotein nitrogen it was found that the 
value for the coefficient of digestibility of protein was not materially 
changed. 
Eight digestion experiments have been made with the grayfish 
and the results obtained for the three-day test period are reported in 
the following table: 
Data of digestion experiments with grayfish in a simple mixed diet. 
Weight 
of food. 
Constituents of foods. 
Experiment, subject, and diet. 
Water. 
Protein. 
Fat. 
Carbo- 
hy- 
drates. 
Ash. 
Experiment No. 535, subject H. R. G.: 
Grams. 
1,409.0 
486. 0' 
400.0 
581.0 
Grams. 
971.2 
366.9 
27.6 
491.5 
Grams. 
244.3 
12.1 
32.4 
2.3 
Grams. 
160.8 
0.5 
53.6 
2.9 
Grams. 
Grams. 
32.7 
Potato 
Crackers 
Fruit 
Sugar 
101.6 
283.2 
82.5 
4.9 
3.2 
1.8 
2, 876. 
64.0 
1,857.2 
291.1 
37.8 
253.3 
217.8 
7.3 
210.5 
467.3 
15.3 
452.0 
42.6 
3.6 
39.0 
87.0 
96.6 
96.7 
91.5 
Experiment No. 537, subject P. K.: 
1,621.0 
507.0 
529.0 
890.0 
1,117.3 
382.8 
36.5 
752.9 
281.1 
12.7 
42.9 
3.6 
185.0 
0.5 
70.9 
4.4 
37.6 
Potato 
Crackers 
105.9 
374.5 
126.4 
5.1 
4.2 
2.7 
3,547.0 
39.0 
2,289.5 
340.3 
17.7 
322.6 
260.8 
8.5 
252.3 
606.8 
598.7 
49.6 
4.7 
44.9 
94.8 
96.7 
98.7 
90.5 
Experiment No. 538, subject C J. W.: 
1,331.0 
452.0 
202.0 
944.0 
12.0 
917.4 
341.3 
13.9 
798.6 
230.8 
11.3 
16.4 
3.8 
151.9 
0.4 
27.1 
4.7 
30.9 
94.5 
143.0 
134.1 
12.0 
4.5 
1.6 
Fruit 
2.8 
2,941.0 
65.0 
2,071.2 
262.3 
27.7 
234.6 
184.1 
13.9 
170.2 
383.6 
14.9 
368.7 
39.8 
Feces 
8.5 
31.3 
89.4 
92.4 
96.1 
78.6 
Experiment No. 547, subject H. R. G.: 
1, 142. 
425.0 
343.0 
599.0 
762.2 
320.9 
23.7 
506.8 
219.7 
10.6 
27.8 
2.4 
132.2 
0.4 
46.0 
3.0 
27.9 
Potato 
88.8 
242.8 
85.0 
4.3 
2.7 
Fruit 
1.8 
Sugar 
2, 509. 
49.0 
1,613.6 
260.5 
26.7 
233.8 
181.6 
7.6 
174.0 
416.6 
9.7 
406.9 
36.7 
Feces 
5.0 
Amount utilized 
31.7 
Per cent utilized 
89.8 
95.8 
97.7 
86.4 
i Jour. Biol. Chem., 16 (1913), No. 3, pp. 3S9-393. 
