DIGESTIBILITY OF FISH. 5 
ration of the fish loaf was identical for the canned and fresh fish. 
In each instance a quantity of the fish to be studied sufficient for the 
entire test period, after being mixed with salt and pepper, was very 
thoroughly and uniformly mixed and baked for two to three hours 
in a moderate oven. Whatever crust formed during baking was 
removed, and the remaining portion was again thoroughly mixed 
in order to secure a uniform product, after which a sample was 
taken for analysis. 
NATURE OF THE DIET. 
Inasmuch as experience has shown that in studying the digestibility 
of a single food it is desirable to supply the food material under con- 
sideration as a part of a simple mixed diet, a suitable basal ration 
was served with the fish loaf. It consisted of boiled potatoes, crackers, 
apple sauce, sugar, tea or coffee, and a little lemon juice as a condi- 
ment in some cases. In accordance with the usual custom, a sufficient 
supply of the special food under consideration (fish loaf) and of the 
other foods was prepared in advance for the whole experimental 
period. The fish loaf was kept in a refrigerator at 15° C. and remained 
fresh and in good condition, as did also the potatoes, which were 
boiled, mashed, and thoroughly mixed to insure uniform composi- 
tion. The apples, which were eaten raw, were of good grade and 
pleasant flavor. The crackers or " biscuits" used were taken from 
a large lot and assumed to be of uniform composition. Though no 
attempt was made to have all eat like amounts, the subjects were 
urged to eat liberally of the fish loaf and moderately of the crackers 
and potatoes, following their individual preferences with respect to 
the apples and the tea or coffee. 
As a whole, the ration, though it contained no added fat and only 
moderate amounts of carbohydrates, was reasonably generous as 
regards protein and energy and was varied enough not to become 
tiresome. 
The food for each man for each meal was weighed in advance and 
kept separate. All remaining uneaten was weighed. The difference 
between the amount furnished and the amount remaining repre- 
sented the amount eaten. 
Samples of the food were reserved for analysis. The small amount 
of lemon juice (on an average, 35 grams per day), which was eaten 
with the butterfish and the Boston mackerel, was disregarded in 
computing the food value of tne diet. 
The feces were collected, sampled, and analyzed by the methods 
followed in the department's digestion experiments, of which the 
present investigation forms a part. 1 
i U. S. Dept. Agr. Bui. 310 (1915), pp. 23. See list on last page. 
