THE DIGESTIVE TRACT OF ELASMOBRANCHS. 9 
Decker (1887) found the stomach of fish to be sometimes neutral, sometimes 
alkaline, and he likewise found that the esophagus of the hake digested fibrin 
much more rapidly than the stomach did. He found in these species, moreover, 
that the esophagus, the intestine along its whole length, the cloaca, and the pyloric 
appendages all produced a ferment comparable to pepsin. 
According to the researches of Knauthe (1898) all the intestinal mucous mem- 
brane of the carp, and especially the anterior portion of the intestine, produces a 
strong tryptic ferment, as does also the liver, or hepato-pancreas. The intestinal 
mucous membrane, except that of the mouth and the hepato-pancreas, produces 
amylolytic and fat-splitting ferments. The bile, he concluded, has of itself no 
digestive action on proteids or fats mixed with extracts of the intestinal mucous 
membrane or of the hepato-pancreas; it augments their action. The bile has, how- 
ever, a diastatic action which is at the maximum at 23° C. 
Bondouy (1899) investigated the function of the pyloric tubes in teleosts and 
came to the conclusion that they played an active part in digestion. They secrete 
trypsin and amylopsin, but no lipase. On the other hand, Bondouy believed the 
pyloric tubes have but little function as absorptive organs. 
Yung (1899) in a very comprehensive and detailed work on elasmobranchs, 
including Scyllium canicula, Acanthias vulgaris, Lamna cornubica, Galeus canis, 
and Carcharias glaucus found that— 
(1) The buceal and esophageal membranes have no digestive action. 
(2) The stomach digests proteids. 
(3) The acidity of the stomach may be as high as 1 per cent. 
(4) The stomach may or may not convert the food into anti-peptone. 
(5) The gastric juice of Scylliwm canicula acts better at 38° C. than at 20° C. 
(6) The formation of pepsin is limited to the stomachice sae. 
Very little study has been given to the physiology of the pancreas of fishes. 
Bernard (1856) proved that the pancreas of the skate converts starch to sugar and 
acidifies fats. Krukenberg (1877), in his werk on selachians, found that the pancreas 
of these fishes was secreting trypsin, the proteolytic ferment, but no amylopsin, the 
starch-splitting ferment, nor lipase, the fat-splitting ferment. Richet (1878), how- 
ever, was unable to find trypsin in the pancreas of selachians, but did find the starch- 
splitting and fat-splitting ferments. Yung (1899), working on Squalus acanthias, 
found amylopsin and lipase, but only occasionally trypsin. Yung attempted to get 
the juice by a fistula, but had little success. His water glycerin extracts were only 
occasionally active. He found that extracts of the spleen aided the activation of the 
pancreas. More recently, Sellier (1902) found that the pancreas of several selachians 
studied by him does not of itself digest proteid, but must be activated by the juice 
of the spiral valve. 
From this synopsis of the literature, it may be seen that there is by no means 
unanimity of opinion regarding the physiology of the digestive tract of fishes. 
