828 REPORT OF COMMISSIONER OF FISH AND FISHERIES. 
There are two ways of studying experimentally the digestibility of 
foods. One is by experiments in artificial digestion, in which the food 
material is exposed to the action of the digestive juices in the labora- 
tory, in apparatus fitted for the purpose. The other is by direct experi- 
ments with man or other animals. 
A series of experiments upon the artificial digestion offish in gastric 
juice has been made by] Messrs. Chittenden and Cummins, and de- 
scribed in the report of the U. S. Commissioner of Fish and Fisheries 
for 1884, p. 1109. 
In the introduction to the account of their work, they speak of these 
experiments as follows-: 
Few experiments appear to have been made on the digestibility of fish ; this is 
the more strange when we consider what an important item of food fish constitutes, 
particularly along our seaboard. * * * As Voit remarks, “ nothing certain 
is known regarding the digestibility of different kinds of fish, although much is said 
concerning it. Probably digestibility is in part dependent upon the nature of the 
fat present and the manner of its distribution ; thus the presence of a difficultly fus- 
ible fat with considerable stearin would tend to hinder digestibility (as in mutton) ; 
the same thing probably occurs when the contents of the sarcolemma are permeated 
with much fat (as in the lobster and eel).” This statement at once suggests the 
probability of great variation in the digestibility of the flesh of any one species, de- 
pendent upon a large number of conditions, which, in the case of fish particularly, 
are somewhat difficult of control ; thus age, sex, food, period of spawning, and length 
of time they have been preserved are a few of the many natural conditions which 
would tend to modify the digestibility of the flesh and render generalizations from 
even a large number of results somewhat uncertain. 
The outcome of their work is expressed thus : 
The results of the analyses show plainly that the method adopted is as good as 
could be expected, for it must be remembered that the two results obtained from each 
sample of flesh are not merely from duplicated analyses, but from duplicated diges- 
tions as well, and in these, extending as they do over 22 hours, with slight variations 
in temperature and agitation, small differences are to be expected. The very great 
divergence noticed, however, in the results obtained from different samples of the 
same species of flesh shows at once that there are other conditions, such as age, etc., 
which affect the digestibility of the flesh more or less, so that in order to obtain results 
from which to draw strict generalizations it would be necessary to experiment with 
fish of different species, of like age, sex, and reared under like Conditions. As samples 
of this we have the very divergent results from two samples of veal, and also of two 
bluefish (88.69 and 73.44). As direct evidence that age, sex, etc., do exert a modify- 
ing influence on the digestibility of flesh, we have three experiments on the flesh of 
the lobster; one with a small young lobster, a second with a large female, and a third 
with a large male of the same species. The duplicate digestions gave fairly concor- 
dant results ; the average relative digestibility being for the young specimen 87.81, 
for the large female 79.06, and for the male 69.13. This shows plainly some modifying 
influence in flesh itself. In composition, so far as the solid matter is concerned, there 
was no appreciable difference in the three samples. Bearing in mind, however, these 
possible variatioqs, it is very evident from our results that the average digestibility 
of fish flesh is far below that of beef similarly cooked. In but two instances, in the 
case of shad and whitefish, does the digestibility of fish flesh approach that of beef, 
although from the average of our experiments several areas easily digestible as 
mutton, lamb, and chicken. 
Pavy states that fish with white flesh, such as the whiting, etc., are less stimulating 
