On the Relation of the Islets of Langerhaiîs to the alveoli of the Pancreas. 203 



by themselves exhibit appearances which most strongly suggest trans- 

 formations in progress. It is undoubted that the two tissues, islets 

 and acini, ai^e frequently in intimate contact; there are places where 

 an acinus appears to pass directly into an islet, where a secreting celj 

 lies adjacent to an islet one. It was doubtless such appearances as 

 these which led Giannelli and Giacomini^), Vincent and Thompson, and 

 Dale to conclude that they represented transitions in progress. While 

 prepared to accept these appearances as in general corroborative 

 of the results of Vincent and Thompson's and of Dale's fasting ex- 

 periments we have important reservations to make. Firstly, with 

 regard to Tropidonotus our admission is made rather hesitatingly on 

 account of the fact that not only alveolus and islet of the pancreas 

 are intermingled in a way suggestive of transformation but pancreatic 

 and splenic tissue are to be found in the region where they are in 

 contact to be equally closely associated. It is quite clear that along- 

 side a single column of pancreatic cells are to be seen undoubted islet 

 cells, and on thfs account taken with the more extensive observations 

 of the forementioned investigators we may assume that transformations 

 in one direction at least take place under certain conditions. We 

 cannot see in this however any argument for the denial of the in- 

 dependence of the two tissues under natural conditions. Prolonged 

 fasting, it appears to us has not been shown to induce trans- 

 formation in the region of the pancreas where islets normally are 

 rare; it has on the other hand been shown that prolonged fasting (in 

 the case of the snake) fails to do so. What these results suggest to 

 us is that at most a transformation (reversionary or degenerative) of 

 alveolar tissue in the vicinity of the islets and possibly proceeding 

 outwards from these takes place. Transformations have not been 

 proved to occur where islets are originally absent. 



The transformation theory as held by these workers involves 

 various difficulties. Some of these have been already indicated in the 

 present paper, but one or two points remain still to be dealt with. 

 These relate specially to morphological questions. Vincent and Thompson 

 state that transformations in experiments with secretin take place so 



^) Quoted by Vincent and Thompson. 



