STUDIES ON THE PANCREAS OF THE GUINEA PIG 385 



in the pancreas after ligation of the duct. They found that the 

 cells of the tubular system to which the pancreas is reduced after 

 this operation were capable of regenerating new acini, or new 

 islets containing both types of cells. 



The fundamental question then that we are required to answer 

 is whether the fully developed acinus cells or islet cells retain 

 any of the potencies which resided in the cells from which they 

 were derived, and if not, at what period in the cytomorphosis 

 of these cells are these potencies lost. Only experiments which 

 yield positive results can give us any light on this question, for 

 it is possible, even though we never find in the normal pancreas, 

 acinus cells developing into islet cells, or vice versa, that the acinus 

 cells nevertheless possess islet potency, and will bring it to expres- 

 sion if the necessary functional demand is made. 



In view of the results obtained by Harvey ('07) and Cade ('01) 

 which have been quoted above I am inclined to think that this 

 view of the developmental potencies of the pancreatic cell will 

 prove to be correct, even though under normal conditions of equi- 

 librium and in view of the regulatory powers which reside in the 

 duct epithelium, these potencies may never under normal condi- 

 tions be brought to expression. 



While admitting the possibility of the transformation of acinus 

 tissue into islet tissue, though insisting that at present we have 

 no actual demonstration of its occurrence, it seems to me that 

 we must also insist that the facts indicate that the normal regu- 

 lation of islet content in the pancreas is not by this method, and 

 that Laguesse's theory of balance which supposes that every 

 acinus in the pancreas may at some phase in its history pass through 

 an islet phase, is untenable. For while Laguesse admits that islets 

 are in direct continuity with ducts, according to his theory, if 

 I have correctly interpreted his explanation, they have this con- 

 nection only because they are formed from acini. Accordingly 

 he is obliged to explain Dewitt's observation of the occurrence of 

 islets in the interstitial tissue of the guinea pig unassociated with 

 acinus tissue, by the assumption that her observation was incom- 

 plete, and that she would have found, if she had studied complete 

 series, small groups of acini attached. I have shown, howev<;r, 



