738 REPORT OF COMMISSIONER OF FISH AND FISHERIES. 
and brought into current use, 44 albuminoids, etc., by difference” will 
be the closest approach to the actual nitrogenous substance. 
The current method of estimating the nitrogenous material is by 
multiplying the nitrogen by 6.25. To this product, various terms, as 
albuminoids, proteids, and protein, are applied. If the figures for 44 albu- 
minoids, etc., by difference” were the exact measure of the nitrogenous 
substance, the difference between them and the product of N x 6.25 
would be the error in computing protein in this latter way. In Table 
2 the ash -f ether extract-!- 44 albuminoids by difference” = 100; and the 
ash + ether extract -f protein (Nx0.25)=a quantity varying more or 
less from 100. On the assumption that the 44 albuminoids by difference” 
represent the actual nitrogenous substance, the variations from 100 in 
the latter figures represent the error in calculating protein by multi- 
plying N by 6.25. 
Of course, the correct determination of actual nitrogenous substance 
involves numerous other questions in addition to those here suggested, 
and first of all the chemical and physiological distinctions between 
the different nitrogenous compounds. But for the present purpose it 
will suffice to take the 44 albuminoids, etc., by difference” as the measure 
of the nitrogenous material. 
The tabular statements which follow give the sum of ash +fat-f- pro- 
tein (N x 6.25) in water-free substance, and of water -f- ash -f fat- -(-protein 
(N x 6.25) in flesh, of the specimens of fishes in Tables 2 and 3, and of 
prepared fish in Tables 4 and 5. For the water-free substance the range 
of the figures is from 97.01 to 116.01, but in the flesh (leaving the pre- 
served fish out of account) the range is only from 99.34 to 102.85, or, 
omitting the skate, to 101.14.* The only cases in which the sum is 
below 99 in the water-free substance of the fresh flesh are those of the 
spent salmon. In these, both nitrogenous substance and fat had been 
reduced during the spawning season. The only ones above 101 in the 
flesh are two specimens of fat salmon, one each of sea bass and turbot, 
several of cod, and one of skate. It is clear that the use of either of 
the figures for protein, Nx6.25, or 44 albuminoids, etc., by difference,” 
for the total nitrogenous substance in the flesh, will involve no very 
serious error except in the last named cases. 
The figures for protein in sea bass, turbot, cod, and especially skate, 
are a little surprising. The question naturally suggests itself whether 
there may not be errors in the analyses. The analytical details show 
that this explanation is extremely improbable. All the nitrogenous 
determinations in the specimens of cod gave large figures. Two deter- 
minations in the specimens of skate gave respectively 16.28 and 16.29 
per cent, in the water-free substance. These figures are so large that 
a third determination was made, with 16.30 as the result. 
. • 
* In our analyses of the flesh of fishes or other animals, when this sum has varied 
much from 1Q0 ; we have repeated the work to make sure of its correctness. 
