DIGESTIBILITY OF FISH. 9 
Summary of digestion experiments with butter fish in a simple mixed diet. 
Experiment No. 
Subject. 
Protein. 
Fat. 
Carbohy- 
drates. 
Ash. 
452 
D.G.G 
R.L.S 
O.E.S 
Average. . . . 
Per cent . 
93.2 
92.2 
89.6 
Per cent. 
94.0 
92.3 
83.3 
Per cent. 
98.2 
97.4 
97.7 
Per cent . 
89.4 
454 
77.1 
455 
75.8 
91.7 
89.9 
97.8 
80.8 
In the digestion experiments made with butterfish, the subjects ate 
an average of 471 grams of fish daily, which supplied 93 grams of 
protein and 23 grams of fat. The protein, fat, and carbohydrates 
of the total diet were found to be 91.7 per cent, 89.9 per cent, and 
97.8 per cent digested, respectively. The values 91.7 per cent and 
89.9 per cent for the digestibility of the protein and fat of the total 
diet become 91.9 per cent and 86.4 per cent, respectively, if allow- 
ance is made for the undigested protein and fat resulting from the 
"basal ration. The estimated value, 86.4 per cent, for the digesti- 
bility of the fat of butterfish is somewhat lower than that of the 
other fish fats here reported. This lower value is no doubt in part 
due to the " heaping up of errors" involved in estimating the diges- 
tibility of a fat of a single food when it represents so small a por- 
tion of the total fat eaten. The subjects reported that they re- 
mained in normal physical condition during the experimental 
periods, except that subjects D. G. G. and O. E. S. reported that 
the diet produced a constipating effect, which was due, no doubt, 
to its very complete utilization. 
GRAYFISH. 
The grayfish (Squalus acantliias, Linnseus), which is very abundant 
and easy to catch, though known to be wholesome, of good flavor, 
and usable for many appetizing dishes, has not been utilized to any 
extent in this country for food purposes, but has been considered 
largely as a source of oil and fish scrap, a fishery industry by-product 
of value for fertilizer material. Recently the Bureau of Fisheries 
has devoted considerable attention to the possible use of this fish in 
human nutrition and is of the opinion that it constitutes a cheap and 
very wholesome food. 
In the literature consulted, no reports were found of the digesti- 
bility of grayfish. In order to judge of the value of the grayfish in 
the dietary, it seemed desirable to obtain information on this point, 
and, accordingly, tests were made in which canned grayfish was 
served in the form of a fish loaf in conjunction with the simple basal 
ration employed in the other tests reported in this paper. The canned 
fish used for this study was supplied by the Bureau of Fisheries and was 
taken to be representative of a large pack put up b}^ a commercial 
concern under the direction of the Bureau of Fisheries. 
