DETERMINATION OE FOOD VAEUE OF PROTEINS. 
179 
column 5 are given figures for amino nitrogen calculated from the data in column 2, 
while the values in the last column were obtained by calculating the per cent calculated 
amino nitrogen of the total soluble nitrogen. 
Table II. — ^Analysis by Sorensen’s Method of Solutions of Cynoscion Regalis 
Hydrolyzed by Trypsin. 
Time in 
hours. 
Quantity 
N/ioNaOH 
required. 
Quantity 
N/io NaOH 
required 
after hy- 
drolysis. 
Average 
size of 
peptids. 
Amino 
nitrogen 
calculated. 
Amino 
nitrogen 
looX 
soluble 
nitrogen. 
c. c. 
c. c. 
0 
24. 85 
125. 0 
5-02 
0-035 
20. 52 
182.8 
536.8 
2.94 
•257 
23. 02 
I 
213-8 
598.0 
2- 80 
.300 
25.87 
5 
293*5 
776.0 
2. 64 
.412 
30. 28 
8 
314.8 
787. 1 
2. SO 
•442 
30.87 
From table i it is seen from the ratio of the soluble to the total nitrogen that the 
fish meat goes very rapidly into solution, 74.32 per cent of the nitrogen being in solution 
at the end of a half hour’s digestion. Solution, however, is not complete in eight 
hours’ time, a fact which is apparently not in harmony with the results of White and 
Crozier,® who found with the proteins they studied that all the nitrogen was in the soluble 
form in four to eight hours. The trypsin used, a commercial sample, was of the same 
activity in both series of experiments. These latter experiments were carried on in a 
medium made alkaline with sodium carbonate, while the experiments described in this 
article required sodium hydroxide for reasons already stated. Schierbeck* has proved 
that the action of tr}7psin in digesting proteins is accelerated by the presence of carbon 
dioxide in solutions which are slightly alkaline, and it is very probably at least 
partly due to this fact that the above differences are found. The variation of the 
proportion of soluble to total nitrogen with increase of time is shown graphically in 
figure I . Extrapolation of the curv^e would indicate that the squeteague would be com- 
pletely dissolved in about 14 hours. 
White and Crozier have shown that their artificial digestion experiments gave results 
agreeing closely with those obtained by metabolism work with dogs, rates of digestion 
of different proteins being in the same ratio to each other. Van Slyke and White,® in a 
study of the relation between the digestion and the retention of ingested proteins, found 
that squeteague is digested more slowly than either beef or cod. From the above facts 
it is fair to conclude that the tardy solution of the squeteague by trypsin shown by our 
data is not alone due to the absence of carbon dioxide, but is a consequence of the 
inherent nature of the protein itseff. 
^ White & Crozier, op. cit. 
^ Schierbeck, N. P.: Ueber den einfluss der kohlensaure auf die diastatischen und peptonbildenden fermente im thierischen 
orgauismus. Skandinavisches Archivfur Physiologic, bd. 3, s. 344-375, 1892. Leipzig. 
c Van Slyke, D. D. & “White, G. F.: The relation between the digestibility and, the retention of ingested proteins. Journal 
of Biological Chemistry, vol. ix, p. 219-229, 1911. Baltimore. 
