34 S. SAGUCHI 



Ultimate fate of islet cells 



Most of the investigators who beheve that islet cells are de- 

 rived from acinus cells seem to admit that there is also a reversal 

 of this transition. According to Lewaschew ('86), the trans- 

 formation begins with the accumulation of the cytoplasm around 

 the nucleus and ends with the appearance of zymogen granules, 

 while the cell boundaries become gradually more pronounced 

 and the cell-body larger. Laguesse ('95-'96, '01) likewise de- 

 scribes that, in this transformation, the cell-body becomes pyram- 

 idal; the nucleus, in which a large nucleolus now appears, 

 passes to the base of the cell and the minute granules of the cj^to- 

 plasm disappear, while zymogen granules are produced. In ad- 

 dition, this author pointed out that it is more difficult to follow 

 'the period of involution' (that is to say, the stage in which the 

 islet returns to the acinus) than 'the period of deconstitution of 

 the acinus,' as the process of involution rapidly spreads over the 

 islet. Laguesse ('01) regards, as transitional, areas that are occu- 

 pied by somewhat larger, indistinctly bounded cells, and by more 

 numerous centroacinus cells, and through which solitary islet 

 cells or small groups of them are scattered. 



It is, as pointed out by Laguesse, a difficult matter to follow 

 the transformation of islet cells into acinus cells; this is perhaps 

 due to the very indistinct nature of change which takes place in 

 the process. Nevertheless, I have been able to detect what are 

 to be regarded as transitional forms between the two tissues. 

 While c cells (figs. 52, 53), as shown under the previous heading, 

 can be considered as derived from 6 or e cells, there exists, on the 

 other hand, no connection between these and any other type of 

 islet cells. They seem rather to be in close relationship with 

 the acinus cells. In the peripheral part of the islet we often find 

 cells with a non-granular, rather transparent cytoplasm, and a 

 more round, vesicular nuclei (figs. 54, 55). These cells may be 

 regarded as transitional between c cells and acinus cells; in com- 

 mon with the former, they contain no zymogen granules and 

 the nucleolus is small, while they have the non-granular cyto- 

 plasm with a small number of mitochondrial filaments charac- 



