522 LECTURE XXII. 



to the group of ferments. It is possible to activate, by means of very 

 small quantities of enterokinase, large amounts of trypsinogen. It is 

 evidently to be considered as a secretion of the intestinal membrane. 

 Intestinal juice, obtained through a fistula, may be added directly to 

 the inactive pancreatic juice. A preparation of enterokinase may also be 

 obtained by scraping off the superficial layers of the intestinal membrane 

 and preparing an extract from these scrapings. The action of the entero- 

 kinase may be well shown by taking some pancreatic juice which has never 

 been in contact with the walls of the intestine, so that the ferments con- 

 tained in it are inactive, 1 and placing some fibrin in it which will not dissolve. 

 Now if we add to another portion of the same juice a few drops of intestinal 

 fluid, or of the extract prepared from the intestinal walls, it will be seen 

 that a piece of fibrin in it dissolves at once. It is not yet perfectly clear how 

 this enterokinase acts. It might be even assumed that there is not a true 

 activating in this case, but that the enterokinase is itself a proteolytic 

 ferment and begins the cleavage of albumin. We have already seen that 

 pepsin attacks the albumin molecule in an entirely different place than 

 does trypsin. It is possible that the enterokinase continues the work 

 of the pepsin and gives up cleavage-products to trypsin which the latter 

 is capable of acting upon. We might also assume that enterokinase 

 attacks trypsinogen itself, modifying it in some way so that trypsin now 

 has certain groups free whereby it can react with albumin, or its cleavage- 

 products. One might be tempted even to assume that between trypsino- 

 gen and enterokinase a union takes place and that active trypsin is 

 thereby formed. If this assumption were correct, then of course the entero- 

 kinase and trypsinogen must always be active in quite definite proportions. 

 This does not appear to be the case, however, for it is possible by means of 

 but very little enterokinase to activate a great deal of trypsinogen. We 

 have here again a reciprocal effect of different organs. The pancreas 

 sends out a zymogen, and the cells of the intestinal membrane form the 

 activator. Pawlow and his student Sawitsch 2 have shown by very pretty 

 experiments that the secretion of the intestine does not invariably contain 

 enterokinase, whether the pancreatic juice reaches the intestine or not. If 

 a canula be introduced in an intestinal fistula, then this mechanical irrita- 

 tion causes a secretion of intestinal juice. Only a small amount of entero- 

 kinase is present in this juice, which consists chiefly of water. In the 

 course of a few hours the intestinal fluid, which is now scanty in amount, 

 contains almost no enterokinase. If now a few cubic centimeters of 

 pancreatic juice be introduced into the intestinal canal, then a juice flows 



1 It should be mentioned here that apparently the ferments in the pancreatic juice 

 always contain a small amount of trypsin in the active form. Cf. B. P. Babkin: Ber. 

 kaiserl. Militararztl. Akad. St. Petersburg 11, Nos. 2 and 3, 93 (1904). 



2 W. Sawitsch: Soc. me"d. russes St. Petersburg (1900-01). 



