74 



THE DIGESTIBILITY OF FISH. 



There are two ways of studying experimentally the digesti- 

 bility of fish as of other foods. One is by experiments in 

 artificial digestion, in which the food material is exposed to the 

 action of the digestive juices in the laboratory, in apparatus 

 fitted for the purpose. The other is by direct experiments with 

 man or other animals. A series of experiments upon the arti- 

 ficial digestion of fish in gastric juice have been made by 

 Messrs. Chittenden and Cummins, and reported in Commis- 

 sioner's Report of the Commission of Fish and Fisheries of the 

 United States for 1884, page 1109. In the introduction to the 

 account of their work these experimenters speak 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 depend- 

 ent upon the nature of the fat present and the manner of its distribution ; 

 thus the presence of a difficultly fusible 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, dependent on a 

 large number of conditions, which, in the case of fish particularly, are some- 

 what difificult of control ; thus age, sex, food, period of spawning, 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 generali- 

 zations 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 digestions as well, and in these, extending as they do 

 over twenty-two hours, with slight variations in temperature and agitation, 

 small differences are to be expected. The very great divergence noticed, how- 

 ever, in the results obtained from different samples of the same species of 

 flesh show 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 examples of this we have the very divergent results from 



