THE DIGESTIVE TRACT OF ELASMOBRANCHS. 21 
Pancreatic jistule.—In order to collect the pancreatic juice a slit was made in 
the abdomen and in the wall of the duodenum of Carcharias littoral/s in such a way 
as to cut the pancreatic duct. Into the central end of the duct was fastened a small 
glass cannula. To the outer end of the cannula was fastened a small sterilized rubber 
balloon. After the sand shark had been sewed up it was set free in a large 
aquarium. In a few days the balloon was taken off and the juice collected with a 
pipette. Asarule the quantity of juice thus collected was small and had no diges- 
tive activity. Owing to the difficulties of keeping the fish alive for a prolonged 
period and of feeding them, I made but six fistulee and then abandoned this kind of 
work for the pancreatic extracts. 
The proteolytic enzyme. Activation of the pancreas.—The pancreas was ground in 
a mortar with glass, and the comminuted mass was treated with water and glycerin. 
After twenty-four hours the mixture was filtered through cotton. To test the diges- 
tive activity of the extracts, at first I used Mett’s tube and fibrin. Finding both of 
these media unsatisfactory, I employed Fermi’s (1902) gelatin method, using 10 per 
cent gelatin and 0.6 per cent carbolic acid. The gelatin was placed in small test 
tubes and the upper layer of the gelatin marked on the tube by means of a blue 
pencil. The amount digested was measured in twenty-four hours if the experiment 
was carried on at the room temperature; in three hours if at 37° C. The pancreatic 
extracts had as a rule very little digestive activity. Accordingly, I added water 
glycerin extracts or water chloroform extracts of the mucous lining of the stomachic 
sac, pyloric tube, duodenum, spiral valve, rectal gland, and spleen to determine 
whether or not any of these extracts would activate the pancreas. Controls were 
made in each case. The results may be found in the table. 
TABLE SHOWING THE ACTIVATING ACTION OF THE VARIOUS Extracts upon Tryptic DIGESTION. 
Sank ees | Pancreas Pancreas Pancreas Pancreas Pancreas 
SIPS OASSE Pancreas. duodenum. spiral valve. rectal gland, spleen. | bile. 
= We | ey . = — 
Carcharias littoralis <...<--....-2.2: 2... 0 or + | 0+ or ++ | t++ 0 or+a 4 }+;— ++6 
Carcharhinus obseurus...........-.----- Oor+ | conn bp 0 or+ | Oor+ 0 or + 
Lamna cornubica ¢ .............---..--- Oor+ | 2 ++ 2 ? | ? 
WORT COs Fc 1 Re Soe OQor+ |0+ or ++ 5 ie poi = } Oor+ Oor+;++4) —; ++? 
Squalus acanthias ....................--. Oor+ | 0 or + ++ 0 or+ | Oor+ } Oor+ 
Raja erinacea ......... .. CR OPe for + + ++ | Oor+ | 0 or + | 0 or + 
BIASVHTIA COMIXUND o) sso cckebs acveak cee 0 ++ | 0 0 0 
| | | 
| | { 
| | | Pancreas | Pancreas 
eee : | , | Spiral Rectal | coc. | and cs ab 
Species. | Bile. jDuode num.| Valve. gland. Spleen. | stomachic poe loric 
| sac. Jee 
| | 
-— eo — ——. _| | — — 
Carchariaslittoralis: -.-<2..52.:.<.2s-s0-s 0 0 0 0 0 + + 
Carcharhinus obscurus -.-...........-.-. 0 0 | 0 0 0 + + 
DBMNA COMUBICA C0215). Fessce costes 0 0 0 0 0 0 0 
AINE) ON CRNIIG YO Sas Sees ee is ne 0 0 | 0 0 0 0 0 
Squalus acanthias ge eat vse Soe 8 0 | 0 | 0 0 0 } 0 0 
Raja erinacea..... 0 0 0 0 0 | 0 0 
Dasyatis centrura. 0 | 0 0 0 0 | 0 0 
| 
+, quantity digested by pancreas. 
++, greater quantity. 
+++, still greater quantity. 
0, no digestion. 
—, less than pancreatic extract alone. 
a Only a few tests were made to determine the activating action of the rectal gland. 
> The bile often increased the proteolytic activity of the pancreas, but occasionally diminished this activity. 
e Only two sets of experiments were made. 
a The spleen occasionally showed activating action. 
