4 S. SAGUCHI 



one hand, acinus cells from which almost all of the zymogen 

 granules have been extruded; on the other, acini in which no 

 lumen is evident. The specific disposition of cells is better 

 seen in the larger islets. The character of the cytoplasm is of 

 greater importance in distinguishing islet cells from acinus cells. 

 Not all of the islet cells contain the minute granules which have 

 been regarded as specific of them. From these considerations it 

 is evident that the large islet is easily defined by the above char- 

 acteristics, but the smaller one, consisting of only a few cells or 

 even of a solitary cell, can be identified only with the greatest 

 difficulty if it contains no specific granules. In other words, it 

 is a difficult problem to decide whether the cells which are inter- 

 spersed among acinus cells and which are devoid of zymogen 

 granules belong to the acinus cells proper or not. The specific 

 granules mentioned above are the only bodies of which we should 

 take account in characterizing any islet cell, other properties 

 being of a rather negative nature, as Benslej^ ('11-' 12) pointed 

 out. We must have more positive identifying characteristics in 

 order to define the islet cell accurately ; the more numerous these 

 are, the more accurately can the cell be defined, so that even a 

 solitary islet cell among acinous cells may be detected with ease. 

 It is then only that the solution of the problem as to a possible 

 transition between the acinus and islet tissue will become an easy 

 one; for the process in question, if there be such, must be accom- 

 panied not only by definite changes in the shape, position, and 

 arrangement of the cells, but also by changes in their internal 

 structure, by which we should be able to trace the gradual dis- 

 appearance of intracellular structures in the acinus cell and the 

 appearance of new cell-constituents which are characteristic of 

 the islet cell, or vice versa. This is the reason why a cytological 

 study of the islet is of great importance in the definition of the 

 islet cell and, consequently, to the question of a transition be- 

 tween the islet and acinus tissue. 



The pancreas of Rana temporaria was selected as the mate- 

 rial for this study as well as for the cytological study of the 

 acinus in a preceding paper (Saguchi, '20). The latter investiga- 

 tion has greatly facilitated not only the study of the minute 



