198 
BULLETIN or THE BUREAU OF FISHEEIES 
poikilothermal animals and the dog were made at 37° C. With one exception 
(viz, peptic digestion in the pickerel, which will be further investigated) digestion 
was more rapid at 37° C. than at room temperature. 
Certain adaptive features are shown in the relation of digestive enzymes to 
food habits. Those animals which include much plant food in their diet show a 
striking difference in the amount of carbohydrate-splitting enzymes from those 
that are wholly carnivorous. In the former amylase and invertase are present in 
'much greater abundance than in strictly carnivorous animals. For example, the 
carp possesses a massive hepatopancreas containing large quantities of amylase, 
while extracts obtainable from the small diffused pancreas of the pickerel digest 
starch very slowly. Furthermore, the mucosa throughout the entire alimentary 
tract in the carp possesses amylase in considerably greater amount than is found 
in the mucosa of the alimentary tract in the pickerel. The bull snake, which is 
entirely carnivorous, possesses no invertase and little amylase as compared with 
that present in the painted and snapping turtles, which often include vegetable 
food in their diets. 
CONCLUSIONS 
1. The reaction of the stomach in each group of poikilothermal vertebrates 
studied is variable, usually being acid when the stomach contains food and nearly 
neutral when the stomach is empty. 
2. No trace of pepsin was found in extracts of esophagus mucosa of pickerel, 
bull snake, and snapping turtle. 
3. The rate of peptic digestion of coagulated egg albumin per given weight of 
moist stomach mucosa is remarkably uniform for the representatives of all classes 
of vertebrates studied. 
4. With one possible exception, which the writer hopes to investigate fvu"ther, 
peptic digestion in all classes of vertebrates was more rapid at 37° C. than at room 
temperature. Tryptic and ereptic digestion were always more rapid at 37° C. than 
at room temperature. 
5. Erepsin is present in as great abundance in the intestinal mucosa of fishes, 
amphibians, and reptiles as in the intestinal mucosa of the dog. 
6. Coagulated egg albimiin is apparently digested equally well by the enzymes 
of fishes, amphibians, reptiles, and mammals. 
7. Amylase is generally present in very small quantity in extracts of mucosa 
from the entire alimentary tract of fishes, amphibians, and reptiles. It is present 
in great abundance in extracts from the hepatopancreas of the carp and from the 
pancreas of Necturus, painted turtle, and snapping turtle. 
8. Invertase occurs in the intestinal mucosa of the carp, blue gUl, painted 
turtle, and snapping turtle, and to a slight extent in the pickerel. There was no 
evidence of invertase in the intestine of the bull snake and Necturus. Lactase was 
not found in extracts of the intestine of the carp, Necturus, or snapping turtle, the 
only animals in which lactase was sought. 
