496 Chemical Study of Food Fishes 
uble in the fat solvent, or carried out with the fat. Accordingly, 
when the fat content of the fish is high the acid value is low, be-. 
cause the proportion of this substance to the total fat is low. 
The Cs of the Vartation in the Distribution of Nitrogen lef 
the Flesh. 
An examination of the nitrogen distribution, as given in Table 
IV, brings out certain facts. It will be observed that not only 
was the amount of nitrogenous substance soluble in cold water 
determined, but also the amount extracted by boiling water. The 
latter solvent was used because of the likelihood of relatively 
large, and possibly significant, quantities of gelatin-like substances 
in fish tissues. The results indicate that the amount is more or 
less constant for fish of the same species but may vary with 
difference in species. This trend is much more clearly shown 
in the amount of nitrogenous substances soluble in cold water, 
where it is seen that the amount of water-soluble nitrogen and 
coagulable nitrogen is fairly constant for the same fish taken at 
different times, while the amounts of these substances may be 
widely different for different species of fish. 
The quantity of nitrogen obtained by aeration is generally ac- 
cepted as indicating the progress of postmortem changes in the 
composition of flesh, especially those of decay as opposed to 
ripening changes. The quantities of ammoniacal nitrogen ob- 
tained from fresh fish of different species become, therefore, of 
importance. It must be remembered that the fish used in this 
study were all very fresh in the market sense of that term. 
Undoubtedly a greater time between catching and analyzing 
elapsed in some cases than in others. Additional observations 
indicate that had all the fish been examined immediately after 
removal from the water the quantity of this constituent would 
have been more uniform in the different samples. However, 
such variations as frequently prevail between the ammoniacal 
nitrogen in the flesh of the fat-poor and fat-rich tissue cannot be 
disregarded, nor can they be referred to decomposition changes. 
A further study of this point is needed. From unpublished data 
we know that fish packed in ice gradually lose some of their am- 
moniacal nitrogen owing to the solvent effect of the water. A 
