DIGESTIBILITY OF FISH. 6 
eral knowledge of the food value of fish and its importance as a 
source of fat and other nutrients in the diet. The results of his 
studies 1 of 50 or • more varieties showed that, on an average, fish 
contains over 18 per cent of protein, and about 4 per cent of fat. 
Generalizing from these data it has been pointed out 2 that fish 
may be divided on the basis of their fat content into three classes: 
Those with over 5 per cent fat such as shad, salmon, butterfish, and 
herring; those containing from 2 to 5 per cent fat such as whitefisli, 
halibut, and porgy; and those containing less than 2 per cent fat such 
as bluefish, haddock, and cod. It is evident that fish, like meat, may 
contribute materially to the fat of the diet, particularly if the fatter 
varieties are eaten. On the basis of the protein they supply they 
also resemble meat, and this is true too with respect to the ways in 
which they are used in the diet. Accordingly, fish should be 
considered as a protein food and classed with the meats. However, 
notwithstanding the fact that protein is essential in the diet and fat 
is supplied in a readily assimilated form in fish, the use of fish is 
small in comparison with the use of beef, pork, and mutton, which 
are also sources of animal protein. The demand for land animal 
" meats" is at present in excess of the supply, while the possible sup- 
ply of fish is believed to be much greater than the present demand. 
In view of the attempts which are being made to interest the 
public in methods of reducing the consumption of meat without 
lessening the nutritive value and attractiveness of the diet, definite 
knowledge of the food value of fish is of especial importance. And 
so, as part of the studies of the food value and uses of fish in the home, 
which are being undertaken, it seemed desirable to study the digesti- 
bility of some varieties of fish taken to be representative of general 
types, including some which are well known and one, grayfish, 
which is comparatively new in the American market. 
DIGESTION EXPERIMENTS WITH MEN. 
Seven young men (medical and dental students) who had gained 
experience in other investigations of like character, served as sub- 
jects in this investigation. They were all normal individuals of good 
health, and reasonably active. During the experimental period they 
were requested to observe their usual routine as regards amount of 
exercise taken, hours of eating, etc. From their knowledge of physi- 
ology and previous experience in this type of work, they were suf- 
ficiently informed of the nature of their duties to appreciate the im- 
portance of carefully following the directions given them. 
For the purpose of this investigation a special fore period and after 
period were not considered necessary, and accordingly the subjects 
* Loc. cit. and IT. S. Dept. Agr., Office Expt. Stas. Bui. 28 (1906), rev. ed., pp. 45-50. 
a U. S. Dept. Agr., Farmers' Bui. 85 (1898), p. 14. 
