[21] }CTTTRTTIVE VALtTE Or* FISH AND INVERTEBRATES. 453 



jonrn in tbe fresb water, wliich sojourn includes the period in which the 

 eggs and milt are developed. The natural result is a very large loss ol" 

 both fat and albuminoids from the body. We have here an exaggerated 

 case of leanness, one in which there is not only a decrease of fat, but of 

 protein also, and the latter in large quantity. 



We thus find in the spent salmon (1) a loss of flesh, so that the 

 flesh of the spent salmon makes up but 56 per cent, of the whole 

 weight of the body, while that of the fat salmon is 62 per cent. ; (2) a loss 

 of both fat and protein of the flesh, so that the flesh which remains in 

 the spent fish contains only 23 per cent, of water-free substance against 

 38 per cent, in the fat flesh. The water-free substance of the flesh makes 

 only 13 per cent, of the total weight of the spent, while it amounts to 24 

 per cent, of the fat, fish. Not only does the whole body lose weight 

 from the fat to the spent condition, but the lighter spent fish contains 

 pound for pound only about half as much nutritive material as the fat 

 fish. The deterioration of the nutritive value of the flesh in the repro- 

 ductive season is, if possible, greater than that of the flavor. The bear- 

 ing of this upon legislation against the capture of the spent fish is very 

 evident. 



COMPOSITION AND RELATIVE NUTRITIVE VALUES OF PISH AS COM- 

 MONLY SOLD. 



As already stated, the specimens were received for analysis in the 

 forms in which they are commonly sold in the markets, some entire, 

 others dressed. The condition of each in this respect is stated in Table 

 IV, which gives the percentage of edible portion — flesh ; and of refuse — 

 bones, skin, entrails, &c. I have included the skin with the refuse, 

 rather than with the edible portion, partly because it seemed best to 

 analyze simply the flesh, and partly because the skin, though it gener- 

 ally contains more or less of nutritive material, is not usually eaten in 

 this country, so far as I have observed. Of course it is eminently desir- 

 able from the chemical standpoint to know more than we do of the com- 

 position of the skin as of the other organs, and the time will doubtless 

 come when increase of population will bring the need of such closer econ- 

 omizing of food material as will lead the people of this country to eat the 

 skin of the fish that come on their tables, thus following the example of 

 the inhabitants of older countries, where rigid economy of food, as ol' 

 other necessaries of life, has long been necessary. Accordingly, in future 

 analyses of fish for determining their economic value, the analyses of 

 the skin will doubtless be desirable, and I do not question that such de- 

 terminations would have added much to the value of the work reported. 

 "With the resources at my command, however,! did not feel myself war- 

 ranted in undertaking them. 



In Table X, I have recapitulated the composition of the specimens of 

 fish as received for analysis, assuming them to represent the composi- 

 tion as ordinarily sold. Here, as previously, the protein is computed on 

 the basis of Table I, i. e., by difference. 



