186 MODERN SCIENCE KEADEK 



to the duodenum and stimulates the epithelial cells to form 

 enterokinase which then activates the trypsinogen to tryp- 

 sin. Assuming that all of these steps are verified by future 

 work, we have in this series of events an excellent example 

 of chemical coordination, that is to say, of coordination 

 effected by chemical stimuli conveyed from one organ to 

 another through the liquids of the body. It may be noted 

 in passing that the epithelial cells of the duodenum under 

 the influence of acids or soaps form an internal secretion, 

 the secretin, while under the influence of the pancreatic 

 juice they produce an external secretion, the enterokinase. 

 It is of course possible that these two different functions 

 are subserved by separate cells, but so far as our evidence 

 goes at present we must infer rather that one and the same 

 epithelial cell gives either an internal or an external secre- 

 tion according to the nature of the chemical stimulus acting 

 upon it. While there can be no doubt at all of the existence 

 of enterokinase and of its wonderful effect in activating 

 almost instantaneously the trypsinogen of the pancreatic 

 juice, much uncertainty prevails as to its nature and its 

 mode of action. Pawlow thought that it belongs to the 

 group of enzymes, and this view has been supported in an 

 almost convincing way by the experiments of Bayliss and 

 Starling. In accordance with this view it is found that 

 the substance exhibits a certain degree of thermolability, 

 being destroyed at a temperature of 67 to 70 C., although 

 in this respect it is less sensitive than most of the well- 

 known enzymes. From this standpoint the action of the 

 enterokinase upon the trypsinogen would come under the 

 general head of catalytic reactions, but here again it is to 

 be observed that its action differs from that of the other 

 enzymes in the great rapidity with which it is completed, 

 a rapidity quite comparable to that of ordinary chemical 

 reactions. Other observers (Dastre and Stassano, Ham- 

 burger and Hekma, Cohnheim) have contended that the 

 enterokinase unites permanently and quantitatively with 

 the trypsinogen, after the manner of an amboceptor and 



