CHEMICAL COMPOSITION OF FOOD-FISHES. 
811 
If we know the actual increase of weight of the flesh, the calculation 
of its absolute changes from the percentages shown by analyses would 
be simple. If there were any constituent whose absolute weight had 
remained constant, comparison of its percentages in the two specimens 
of flesh would give the desired data. I am inclined to think the pro- 
tein very nearly fulfills this condition. The statements above show the 
probability that some of the protein, i. e ., nitrogenous material, left the 
flesh and went into the liquids during the floating, but this quantity, 
though it may have been considerable in comparison with the amount 
in the liquids before dialysis, must, it would seem, have been very small 
in comparison with the amount of nitrogenous material in the flesh. 
Of course this is only an assumption, but it seems a very probable one. 
The loss by metabolism and excretion of metabolized products in 
forty-eight hours by so inactive an animal as the oyster we should 
naturally expect to be very small indeed. Dr. Conn tells me that the 
animals live and thrive for months when their only source of nourish- 
ment is from water by which they are moistened only at long intervals 
and for a few hours at a time by exceptionally high tides, circum- 
stances which preclude anything more than an extremely small food 
supply and in which, consequently, the metabolism must be very slight. 
In brief, it seems to me that we shall probably not go far astray in 
assuming that the whole amount of nitrogen given off from the body 
during the forty -eight hours in which the dialysis is taking place must 
be very small indeed as compared with the amount in the body (flesh) 
- of the animal. 
If, then, we assume that the amount of nitrogen remains constant 
during the dialysis the decrease in percentage of nitrogen, i. e ., protein, 
in the flesh during dialysis may be considered as due to the increase of 
total weight of flesh and will furnish a measure of that gain in weight. 
Thus in the body of the James River oyster the percentages of pro- 
tein before and after dialysis were, respectively, 10.63 and 8.79. That 
is to say, assuming the body to have neither gained nor lost protein 
during dialysis, 100 parts which before dialysis contained 10.63 parts 
of protein must during dialysis have increased to such a weight as to 
reduce the percentage to 8.79, and this weight must be to 100 as 8.79 to 
10.63, which would give 120.93 as the weight after dialysis of the same 
flesh which before dialysis weighed 100. Accordingly, if we take the 
percentages found by analysis in the dialyzed flesh and multiply them 
by 1.2093, we shall have the absolute quantities of each of the several 
constituents after dialysis in the flesh which before dialysis weighed 
100, and the quantities of whose constituents are the percentages shown 
by the analysis. Thus the 77.99 per cent, of water multiplied by 1.2093 
give 100.09, and 100.09 — 77.99=22.10, the absolute gain of water in the 
dialysis. As 22.10 is 28.34 per cent of 77.99, the water was increased 
by 28.34 per cent of its amount by the dialysis. The table which fol- 
lows gives a statement of calculations made in this manner. 
