CYTOLOGICAL STUDIES OF LANGERHANS's ISLETS 5 



structure of the islet cells, but also the solution of the question 

 of a transition. The methods employed for fixing and staining 

 were the same for both, and this has enabled me to compare the 

 structures thereby brought to light, both in acinus cells and in 

 islet cells, in one and the same preparation. 



MINUTE STRUCTURES OF ISLET CELLS 



Historical 



The islet cells, though they have long been a problem for ob- 

 servers, have not yet been satisfactorily investigated in regard to 

 their minute structures, at least not by the newer cytological 

 methods. In looking over the hterature, one finds several ref- 

 erences to the cytoplasmic structure. These briefly may be 

 summarized as follows: 



Since Langerhans's time, it has been frequently stated that 

 the islet, either in whole or in part, consists of clear, transparent 

 cells which are devoid of zj^mogen granules. Lewaschew ('86) de- 

 scribes two kinds of islet cells, both of which have the transparent 

 cytoplasm, but which can be distinguished from each other by 

 the shape and mode of delimitation of the latter. 



Massari ('98), Diamare ('99), Schulze ('00), Levi ('04), Vin- 

 cent and Thompson ('07), and others distinguish between two 

 kinds of islets cells, one of which stains more heavily than the 

 other. Vincent and Thompson, among others, pointed out that 

 this difference is observed in the pancreas of various vertebrates; 

 they designated the faintly staining islet as the leptochrome tissue 

 and the heavier staining one as the bathychrome. According to 

 these authors, the former constitutes the well-known islet of 

 Langerhans; the latter, in mammals, consists of small groups of 

 cells or even of solitary elements scattered throughout the se- 

 creting alveoli, while in birds, reptiles, and amphibia, it forms a 

 solid mass of cells. The bathychrome tissue shows a remark- 

 able tendency to form syncytium and stains deeply with ordinary 

 dyes; this is especially true of the Flemming fixation. 



Some investigators, on the other hand, have found special 

 granules in some of the islet cells. Laguesse ('93) stated that 



