184 
BULLETIISr OF THE BUREAU OF FISHERIES' 
RESULTS AND DISCUSSION 
REACTION IN THE DIGESTIVE TRACT 
The reaction in the stomach and intestine was found to be exceedingly variable 
even among the animals of the same species, apparently depending upon the func- 
tional state of the organ. In the stomachs of all groups of poikilothermal verte- 
brates the reaction varied from about neutrality to an acidity sufficient to turn 
Congo red purple, a pH of about 4. Generally the acidity was higher when the 
stomach contained food, subsiding to near neutrality when empty. The greatest 
acidity was observed in a bull snake, the stomach of which contained the remains 
of two mice, still largely intact, which had been devoured two days before killing. 
Here the hydrogen ion concentration was almost pH 3, while no acidity could be 
demonstrated in the stomach of a bull snake that had been fasting. In the stomachs 
of garter snakes that had swallowed frogs one to three hours before being opened 
a similar region of acidity was observed around the frogs. These findings agree 
with the early statements relating to fish. Tiedemann and GmeHn (1827) and 
Decker (1887) observed that contents of full stomachs of fish would always redden 
blue litmus, while the reaction at other times was neutral, slightly acid, or even 
very slightly alkaline. 
The contents of the intestine also exhibited similar reaction in different classes 
of vertebrates. The reaction was in most cases about neutral, sometimes devia- 
ting to the acid side and sometimes to the alkaline, more frequently being slightly 
alkaline. The highest alkalinity, pH 8 to pH 8.4, was frequently observed in the 
smaU intestine of turtles. In the carp, which has no stomach but a long, compara- 
tively undifferentiated alimentary canal, the reaction was in most cases slightly 
alkaline or neutral, though occasionally slightly acid. Variations in reaction of 
different parts of the tract of this fish were common. Acid reaction was observed 
most frequently in the posterior end of the intestine. Such acidity may be due 
to bacterial fermentation, which would perhaps take place to the greatest extent 
in this region, since it contains food materials that have remained longest in the 
intestine. It may be that the carp, an animal of rather sluggish habits, which stuffs 
its entire alimentary canal with vegetation, muddy algse, minute insect larvse, 
etc., depends more or less upon bacterial action as a material aid in the digestion 
of its food. 
PEPTIC DIGESTION 
ESOPHAGUS 
Extracts of the esophageal mucosa of the pickerel, snapping turtle, and buU 
snake produced no increase in tyrosine or amino acid when allowed to act upon 
coagulated egg white at a pH of 3 for eight days. Absence of pepsin from the eso- 
phagus of these is in agreement with the known facts of their histological structure. 
Oppel (1897) cited observations of different workers upon numerous species of 
fishes, including the pickerel, and made the generalization that no glands are 
present in the esophagus of fishes. In sturgeons, however, gastric glands extend 
up into the esophagus (Kingsley 1917). In the amphibians glands are known to 
exist in the esophagus of Proteus anguineus, Necturus maculosus, and Rana, occurring 
most abundantly in the region of the esophagus nearest the stomach (Oppel, 1897). 
