CH. XXXII.] ENTEROKINASE AND EREPSIN 497 



If fresh pancreatic and intestinal juices are mixed together, the 

 result is a powerful proteolytic mixture, though neither juice by itself 

 has any proteolytic activity. 



Pawlow speaks of the substance in the intestinal juice which has 

 this action as a " ferment of the ferments," and has named it entero- 

 kinase. It mainly reinforces tryptic activity, but also has a similar 

 though slighter energising influence on the fat-splitting ferment. 



Starling, like Pawlow, worked with clogs, and has confirmed his 

 main results. A valuable contribution to the same subject has also 

 been made by Hamburger. He has had the unusual opportunity of 

 examining human succus entericus. It became necessary in a patient 

 for surgical reasons to isolate a loop of the small intestine, and this 

 loop continued to discharge intestinal juice to the exterior for some 

 time after the operation. He finds that this juice, like that of the 

 dog, contains a substance which renders pancreatic juice active. He 

 could not find that it exercised any energising influence on the 

 fat-splitting and amylolytic ferments of the pancreas, but its action 

 on the tryptic ferment was most marked. His quantitative experi- 

 ments do not bear out Pawlow's view that the active substance 

 in the intestinal juice is a ferment, for it is unable like a ferment to 

 act on an unlimited amount of pancreatic juice. Delezenne also 

 thinks it is not a ferment, but compares it to the immune body or 

 amboceptor which enables hsemolysins to become effective (see p. 443). 

 Starling, however, supports Pawlow's view ; provided sufficient time 

 is allowed to elapse, it will energise any amount of pancreatic juice. 



Another discovery in connection with succus entericus has been 

 made by Otto Cohnheim. The juice has no action on native proteids 

 like fibrin and egg-white,* but it acts on proteoses and peptone. It 

 rapidly breaks them up into simpler substances of which ammonia, 

 leucine, tyrosine, and the hexone bases have been identified. Cohn- 

 heim has named the ferment to which this is due erepsin. Ham- 

 burger found that erepsin is also present in the human juice ; it is 

 not identical with enterokinase because erepsin is destroyed by heat- 

 ing the juice to 59 C. for three hours ; enterokinase is not destroyed 

 until the temperature is raised to 67 C. Other observers have con- 

 firmed the discovery of erepsin, but have found that it or a similar 

 ferment is present in most tissues; it is most abundant in the 

 kidney (Vernon). 



The products of erepsin action are not discoverable in the blood 



* Cohnheim has investigated the action of erepsin on a large number of proteids : 

 it acts energetically on proteoses, peptone, and protamines : on histone, which 

 occupies an intermediate place between protamines and the proteids proper, it has a 

 slight action. On the proteids proper it has no action, with the single exception of 

 caseinogen, which is speedily broken up into simple substances ; this opens up the 

 interesting physiological possibility that the suckling infant is able to digest its 

 proteid nutriment even if pepsin and trypsin are absent. 



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