178 
BULLETIN OF THE BUREAU OF FISHERIES. 
and analyses run in duplicate for the time periods of i , 2, 5, and 8 hours, respectively. 
A sample similar to the above but containing no trypsin was also prepared and analyzed 
with the others according to the following method: At the end of the desired time of 
digestion, the mixtures were filtered and aliquot portions of the filtrate taken for the 
various tests; 10 c. c. were used for the determination of total soluble nitrogen by the 
Kjeldahl method; 10 c. c. for the amino nitrogen b}^ Van Slyke’s method; 20 c. c. were 
treated with 10 c. c. of 40 per cent formaldehyde solution and titrated to a distinct 
pink color with N/io sodium hydroxide solution. We found that in every case a distinct 
end point was obtained, duplicate analyses agreeing within 0.2 per cent. Finally, 
10 c. c. of the filtrate from the digested fish were completely h5'drolyzed by prolonged 
digestion on the water bath with 40 c. c. of concentrated hydrochloric acid. This solution 
was evaporated to dryness, made up to 50 c. c. with water, 10 c. c. tested for amino 
nitrogen by Van Slyke’s method, and 20 c. c. analyzed for amino acids by Sorensen’s 
method. 
All the results as obtained above were corrected for amino nitrogen before and after 
complete hydrolysis, for total soluble nitrogen, and for amino acids as determined by 
titration with caustic soda, by carrying through the same experiments with trypsin and 
alkali, but with no protein. Correction was also made for the alkali required to 
neutralize the formaldehyde solution. 
In table i are presented the results obtained by applying Van Slyke’s method to 
the tryptic proteolysis of squeteague. The average size of the peptides was calculated 
by dividing the amount of amino niti'ogen present after complete hydrolysis with hydro- 
chloric acid by that in the solution before such hydrolysis. The last two columns of 
data show the increase with time of proportion of soluble to insoluble nitrogen and of 
amino to total soluble nitrogen, respectively. The average results of duplicate analyses 
are given. 
Table I. — Total and Amino Nitrogen in Solutions of Cvnoscion Regalis 
Hydrolyzed by Tr\t*sin. 
Time in 
hours. 
Soluble 
nitrogen. 
Insoluble 
nitrogen. 
Amino 
nitrogen. 
Amino 
nitrogen 
after hy- 
drolysis. 
Average 
size of 
peptids. 
Soluble 
Amino 
total 
nitrogen. 
soluble 
nitrogen. 
0 
0. 170 
1-330 
0.017 
0. 056 
3-29 
11.32 
10. 00 
I- IIS 
•38s 
. 230 
.464 
2.02 
74-32 
20.63 
I 
I-I 7 S 
•340 
.250 
.464 
1.86 
78.34 
21. 27 
2 
1-173 
•327 
. 2R9 
.464 
1. 61 
78. 20 
24. 63 
5 
1.361 
•139 
•357 
90.72 
26. 23 
8 
1.432 
.068 
.406 
. 646 
I- 59 
95-45 
28.3s 
In table ii are given the average results of the analysis of the proteolyzed solutions 
according to Sorensen’s method. In column 2 the figures represent cubic centimeters 
of N/io sodium hydroxide solution required for neutralization after addition of formal- 
dehyde solution. Column 3 is the same for the solutions after complete hydrolysis with 
hydrochloric acid. The next column gives the ratio of the latter to the former. In 
