CHEMICAL COMPOSITION OF FOOD-FISHES. 
829 
and lighter to the stomach, or more easy of digestion, than lish with more or less red 
flesh, as the salmon. Our experiments confirm this statement so far as digestibility 
is concerned. Thus the average digestibility of the salmon and trout is considerably 
below the average of the more digestible whitefish. The difference between the 
digestibility of the light and the dark meat of the same flesh is somewhat striking, as 
in the case' of the shad, where the digestibility of the former was found to be 97.25, 
as compared with beef, while the dark flesh was 87.32, A similar difference, though 
very much smaller, is to be noticed between the light and dark meat of the chicken. 
This difference in digestibility is in part due, without doubt, to the amount of fat 
present, for, as Pavy states, in the flesh of the white fish there is but little fat, it 
being accumulated mainly in the liver of the animal, while in red fish there is more or 
less fatty matter incorporated with the muscular fibers. For a similar reason eels, 
mackerel, and herring are, according to Pavy, less suited to a delicate stomach than 
some of the white fish, and our experiments show that in digestibility two of them 
stand below the more digestible white fish; mackerel, however, from our single 
experiment with the white portion of the flesh, showed a comparatively high diges - 
tibility. In all of our experiments, however, with white fish we rejected the outer 
layer of dark flesh, except in the case of the shad. The varying differences in 
digestibility are not to be considered as due wholly to differences in the amount of 
fat in the flesh; thus the flesh of fresh cod coutains but little fat, and yet it is one 
of the most indigestible of the white fish experimented with. This agrees with 
Pavy’s experience “ that it is a more trying article of food to the stomach than 
is generally credited.” Again Pavy makes the following statement, based on his 
experience in fish dietetics: “Of all fish the whiting may be regarded as the most 
delicate, tender, and easy of digestion.” “ The haddock is somewhat closely allied, 
but is inferior in digestibility,” while 4 ‘ the flounder is light and easy of digestion, but 
insipid.” With all these statements our results agree perfectly, assuming the white 
fisli of our experiments to be analogous to the English whiting. 
It thus appears that Messrs. Chittenden and Cummins found consid- 
erable divergence in the digestibility of the flesh of fishes of different 
kinds. This they attribute in part to the varying proportions of fat 
(the fatter fish being less digestible) and in part to other characteris- 
tics of the flesh. My own impression is that experiments on the actual 
digestion in the alimentary canal, in which other juices as well as the 
gastric come in play and other conditions are different, would show less 
difference in the digestibility of fish of different sorts than Chittenden 
and Cummins found in their experiments in artificial digestion with 
gastric juice alone, and also that there would be less variation in actual 
quantities and nutritive material digested than the statements made 
by those authors would imply; for we must not forget the distinction 
between the quantity digested and the ease of digestion. But of course 
this is a matter to be determined by actual experiments and observation- 
The ways for testing the digestibility of foods by men and animals 
are very ingenious and interesting. Physiologists use the salivary 
glands, stomach, or intestines of a living animal much as chemists do 
their bottles, retorts, and test tubes. It is easy to get into the way of 
regarding an animal as simply an organism manifesting certain reac- 
tions under given conditions, and in not a few European laboratories 
a janitor is readily induced by the price of a few months 7 supply of 
beer, or a student by his scientific ardor, to take this same altruistic 
view of his own physical organisms. In the German laboratories par* 
