24 S. SAGUCHI 



there are found cells which contain both specific granules and 

 mitochondrial filaments. The relation of c cells to other types 

 of islet cells is a problem which is difficult to solve. From the 

 granular appearance of their protoplasm and the absence of 

 mitochondrial filaments, it seems not unlikely . that they bear 

 some relation to b cells. But the possibilitj^ of a transition be- 

 tween e and c cells is by no means to be excluded. 



Summarizing the above observations upon the cytological 

 character of the islet cells, we come to the conclusion that the 

 five types of islet cells are connected with one another by all 

 grades of transition: a cells pass into b cells and the latter into 

 e cells ; on the other hand, e cells pass into b cells and perhaps into 

 c cells. The d cells and e cells have many characteristics in com- 

 mon, so that a transition between them is quite conceivable. I 

 am of the opinion that the d cell is a resting phase of the e cell; 

 the nucleolar hyperchromasy of the nucleus and cytoplasm with 

 abundant production of mitochondrial filaments strongly suggests 

 this view. From these considerations it must be admitted that 

 a cells and c cells, though connected with 6 or e cells, have no re- 

 lation to any other types of islet cells; in other words, they can- 

 not be regarded as intermediate between any two types. Are 

 they to be regarded as a resting phase of other types of islet 

 cells, or as an intermediate condition between the islet cell and 

 some other cell which forms a constituent of the pancreas? To 

 solve this complex and difficult question it is not sufficient to in- 

 vestigate the islet tissue only, but other elements of the pancreas, 

 especially the acinus cells, must be subjected to a careful exami- 

 nation. If, in this way, a transition between the a cells or c 

 cells and the acinus cells can be traced, there can be no doubt 

 that the islet is not an independent organ. A discussion of this 

 matter wdll be taken up in connection with the relation between 

 islet and acinus cells. 



DISTRIBUTION OF ISLET CELLS IN THE PANCREAS 



Since the pancreas of the frog is small, it is an easy matter to 

 cut cross-sections through it and to examine the distribution of 

 the islet cells. If search is made in such sections for cells which 



