30 S. SAGUCHI 



granules cannot always be regarded as transitions, for the resting 

 acinus cells and centroacinus cells may have the same appear- 

 ance; a distinction between the two is often made with difficulty 

 in cases where the islet cells are interspersed among acinus cells. 

 Cells containing, on the one hand, minute granules which are 

 assumed to be a characteristic constituent of the islet cell, and, 

 on the other, zymogen granules, as has been described by La- 

 guesse, can certainly be considered to be transitional between 

 the acinus and islet tissue. It must be borne in mind, however, 

 that there are islet cells in which the minute granules cannot be 

 manifested and the protoplasm of which, in ordinary preparations 

 exhibits a clear, transparent appearance. 



That the islet cells can be characterized by the presence not 

 only of minute granules, but also of several other protoplasmic 

 structures, has been mentioned above, and if there be a trans- 

 formation of acinus cells into islet cells, the formation of the 

 specific cytoplasmic constituents in the latter cells and the dis- 

 appearance of those in the former must take place in a visible 

 manner; thus the general process of transformation can be fol- 

 lowed more accurately than with any other methods. For this 

 reason as many recent cytological methods as possible must be 

 employed in the investigation of the islet, and, at the same time, 

 the minute structures of the acinus cells must be taken into 

 account. 



From a careful study I have come to the conclusion that there 

 is a transformation of the acinus cell into the islet cell, whereby 

 not only the cell-body and the nucleus change shape and position, 

 but the intracytoplasmic structures also undergo a series of defi- 

 nite alterations. This process of transformation may be divided 

 into two stages: 



First stage. The acinus cells which are about to transform 

 into islet cells gradually decrease in volume, and some of them 

 take a rather elongated form as if from compression between the 

 neighboring cells (figs. 3, A', 8, 9). Concomitant with this 

 change, a gradual reduction in the number of zymogen granules 

 takes place. The nucleus seems to undergo no remarkable 

 change in size, although it takes the form best adapted to that 



