determination of food value of proteins. 
i8i 
only approximate figures are expected on assuming the presence of one amino group 
for every carboxyl group indicated by the sodium hydroxide required. The amino 
nitrogen thus estimated is regularly greater than that determined by the nitrous acid 
method, and the peptids as computed are about 1.5 times as large. It is possible that 
in such calculations , ./ 
thiseffectis produced 
by the presence 
the presence of 
such monamino- 
dicarboxylic c o m - 
pounds as glutamic 
acid. The discrep- 
ancy in the results 
is not of such a mag- 
nitude as to prevent 
deducing rigid con- 
clusions concerning 
the rate and course 
of digestion of such 
proteins as the one 
under investigation. 
SUMMARY. 
3 ^ 
30 
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zo 
15 
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/?ouns 
I. Sorensen’s 
method for the de- 
termination of amino 
acids was applied to 
a study of the tryptic 
proteolysis of Cynos- 
cion regalis. The re- 
sults were regular 
and in accord with 
those obtained by the 
nitrous acid method 
for the analysis for 
amino nitrogen. A practical method for the determination of the food value of proteins 
has therefore been developed. 
2. The relatively low rate at which the protein is made soluble agrees with the 
results of metabolism experiments. 
3. Very low cleavage products are formed as soon as the protein goes into solution, 
the average size of the peptids being 2.02 after a half hour’s digestion. 
4. There is a very stable nitrogen complex which is not attacked by trypsin. 
0 / Z 4 6 
Pig. 2. — Change of the per cent of amino nitrogen of the soluble nitrogen during the time of 
proteolysis. 
