1912.] Islets of Langerhans to the Pancreatic Acini. 85 



both acinous and islet tissue were apparently in process of destruction, and 

 in both the characteristic appearance of normal islets was for the most 

 part absent. It is unfortunate that the duct ligation experiment could not 

 have been extended, but it is possible that some communication between the 

 pancreas and bowel was being established. 



Though a number of investigators have succeeded in reducing the pancreas 

 to a condition in which no zymogenous tissue remained, and only islets 

 were left, without bringing on diabetes, they have not been able to apply 

 the final test of discovering whether the animal could live without what 

 remained. This is true of the experiments of Laguesse, and others, on 

 duct ligation in the rabbit, in which removal of the pancreas seems to be 

 impossible. I believe also that no such final test has been applied to the 

 dog with a satisfactory proof of the existence of only genuine islet tissue 

 in what remained. Until such final proof is given, the association with the 

 islets rather than the acini of an important sugar function is only implied. 

 Nor does my incomplete investigation more than suggest this conclusion. 



Conclusions. 



1. The islets of Langerhans contain specific granules which allow of their 

 positive identification. 



2. There is no alteration in the islets, nor any evidence of conversion of 

 acinous to islet tissue, under prolonged stimulation with secretin. On the 

 contrary, the distinction between the two tissues is, under appropriate 

 staining methods, more clear than usual. 



3. There is no evidence of the conversion of acinous to islet tissue or the 

 reverse, when only a small part of the pancreas is left to support life. 



4. There is evidence that islet cells are reduced to a condition in which 

 they appear similar to duct cells under these conditions, the first change being 

 a disappearance or discharge of the granules characteristic of the B cells of 

 Bensley. 



5. There is evidence of an increase of duct tissue under the same condi- 

 tions, but no evidence that this tissue produces new islets or takes up their 

 function. 



6. There is no positive evidence that islets are of vital importance to 

 carbohydrate metabolism, but as between islet and acinous tissue the 

 evidence favours the islet. 



