96 



SCIENCE 



[N. S. Vol. XXXI. No. 786 



lows: Hydrochloric acid formed in the 

 stomach and brought into the intestine 

 with the chyme stimulates the epithelial 

 cells of the intestine to form secretin and 

 to pass it into the blood. The secretin 

 conveyed by the blood to the pancreas 

 stimulates this organ to secrete pancreatic 

 juice. The pancreatic juice is carried to 

 the duodenum and stimulates the epithelial 

 cells to form enterokinase which then acti- 

 vates the trypsinogen to trypsin. Assum- 

 ing 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 coordina- 

 tion 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 duo- 

 denum under the influence of acids or 

 soaps form an internal secretion, the secre- 

 tin, while under the influence of the pan- 

 creatic 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 epithe- 

 lial cell gives either an internal or an ex- 

 ternal secretion 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 won- 

 derful effect in activating almost instan- 

 taneously the trypsinogen of the pancre- 

 atic 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 ex- 

 periments 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 tem- 

 perature of 67 to 70° C, although in this 



respect it is less sensitive than most of the 

 well-known enzymes. From this stand- 

 point the action of the enterokinase upon 

 the trypsinogen would come under the gen- 

 eral 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 com- 

 pleted, a rapidity quite comparable to that 

 of ordinary chemical reactions. Other ob- 

 servers (Dastre and Stassano, Hamburger 

 and Hekma, Cohnheim) have contended 

 that the enterokinase unites permanently 

 and quantitatively with the trypsinogen, 

 after the manner of an amboceptor and 

 complement, to form a new and active 

 compound, the trypsin, and the whole re- 

 action has been still further complicated 

 by the discovery (Delezenne) that the 

 trypsinogen may be activated by calcium 

 salts without the presence of enterokinase. 

 The action of the calcium requires some 

 time for its development but when it oc- 

 curs it takes place not gradually but ab- 

 ruptly, just as in the case of the activation 

 produced by enterokinase. The further 

 fact stated by Delezenne that the entero- 

 kinase itself needs the presence of calcium 

 salts before it acquires the property of 

 affecting trypsinogen suggests naturally 

 the thought that the action of the entero- 

 kinase may be at bottom another ease of 

 calcium activation. Pozerski states that in 

 the inactive pancreatic juice obtained by 

 injections of secretin calcium is not pres- 

 ent; whereas in the active juice following 

 upon the use of pilocarpin, calcium is con- 

 tained, and the digestive action of the juice 

 runs parallel with the content in calcium. 

 But whether the enterokinase acts as a 

 ferment, or an amboceptor, or a calcium 

 carrier it constitutes a special type of 

 organic activator and this fact suggests the 

 possibility that other processes in the body 

 may be controlled by similar compounds. 



