246 PHYSIOLOGY OF ALIMENTATION. 



The secretion of the large intestine is small in amount and 

 rich in mucin. It is stated to be alkaline in reaction, and to 

 contain no ferments in sufficient amount to be of physiologi- 

 cal importance. The large intestine acts chiefly as an organ 

 of absorption. 



4. Enterokinase. This is the term given by PAWLOW to a 

 substance discovered by SCHEPOWALNIKOW in the mucous 

 membrane of the small intestine which has the interesting 

 property of inaugurating or at least of increasing enormously 

 the proteolytic power of the pancreatic juice as it flows from 

 the gland. 



We are probably correct in believing that neither the pan- 

 creas nor the pancreatic juice obtained directly from the 

 pancreatic duct contains any alkali-pro teinase (trypsin), but 

 only a substance (the so-called proferment or zymogen) which 

 can be converted into tHis ferment through contact with 

 enterokinase. Under physiological conditions this contact 

 with enterokinase is established as soon as the pancreatic 

 juice flows over the mucous membrane of the small intestine, 

 the walls and secretions of which contain this activating sub- 

 stance. The amount of mucous membrane necessary to 

 bring about at least some activation of the otherwise inactive 

 pancreatic juice is very small according to DELEZENNE and 

 FROUIN'S 1 experiments. In the ordinary method of making 

 a pancreatic fistula according to the method of HEIDENHAIN 

 and PAWLow, 2 by cutting out a small portion of the mucous 

 membrane surrounding the pancreatic duct and sewing this 

 into the edge of the abdominal wound, the escape of the pan- 

 creatic secretion over this bit of mucous membrane is sufficient 

 to give it well-marked digestive properties for proteins. If 

 the escape of the juice across the transplanted mucous mem- 

 brane is avoided by inserting a cannula into the duct above 



1 DELEZENNE and FROTJIN: Compt. rend, de Soc. biol., 1902 

 CXXXIV, p. 1524. 



2 See p. 215. 



