190 
BULLETIN OF THE BUREAU OF FISHERIES 
EREPTIC DIGESTION 
Up to the present time the general occurrence of erepsin in the intestinal 
mucosa of lower vertebrates has not been demonstrated. In fact, most of the 
investigations that have been made of digestive enzymes in lower vertebrates 
were made before the discovery of erepsin by Conheim (1901). The only record 
of ereptic digestion in poikilothermal vertebrates which the writer has been able 
to find was a brief statement by Kriiger (1905) that an extract could be obtained 
from the small intestine of Gadus fnorrhua, which showed characteristic erepsin- 
like activity. 
Tables 5 and 6 show the results obtained for ereptic digestion by extracts of 
intestinal mucosa from representatives of different groups of vertebrates. In 
Table 6 parallel experiments with digests at room temperature and at 37° were 
made. In Table 5 all experiments were made at room temperature. Since erepsin 
digests casein but not other native proteins, with the exception of histones and 
protamines, casein was used as a substrate. The digests were all made alkaline 
with 0.2 N sodium carbonate to an initial pH as low as 8.4, thus preventing action 
by autolytic enzymes and pepsin. Parallel digests with coagulated egg albumin 
were used as controls against any tryptic digestion. It will be noted that in this 
case, as in tryptic action, the amino acid increase was comparatively high. 
The data presented in Table 5 show that erepsin is present in the intestinal 
mucosa of the representatives of all classes of poikilothermal vertebrates in as 
great an abundance as in the intestinal mucosa of the dog. In the carp ereptic 
digestion was greatest in extracts from the anterior end of the alimentary tract, 
gradually decreasing posteriorly. In the pickerel a definite though small increase 
in both amino acid and tyrosine in the control digest probably indicates a trace of 
tryptic digestion. This may have been a factor in the high rate of casein cleavage 
for the pickerel. Where the animal possessed a well defined small and large in- 
testine, digests using extracts of mucosa from the small intestine only are included 
in the tables. Extracts from the mucosa of the large intestine of the snapping 
turtle, an animal in which the large and the small intestine are clearly defined, 
also produced a high rate of ereptic digestion. Erepsin has likewise been reported 
present in considerable quantity in the large as well as small intestine of the rabbit 
(Glaessner, 1910). 
