CYTOLOGICAL STUDIES OF LANGERHANS's ISLETS 23 



4. The d cells are few in number and are interspersed among e 

 cells (figs. 1, d, 20, 33). They differ from the latter in the fol- 

 lowing details: 1) the number of lipoid corpuscles is smaller than 

 the e cells (figs. 1, d, 33); 2) the urano-argentophile apparatus 

 seems to occur in the form of delicate filaments (fig. 33) ; 3) the 

 protoplasm of the d cells stains more deeply and appears darker 

 in iron-hematoxylin or uranic nitrate-silver preparations; 4) the 

 mitochondria are more abundant than in e cells (fig. 1, d); 5) 

 the nucleus exhibits a distinct network with closer meshes (fig. 

 1, d). 



5. The e cells contain very few if any specific granules and 

 thus the cell-body has a more transparent appearance. The 

 most characteristic feature of the protoplasm of the e cells is the 

 great abundance of mitochondrial filaments (figs. 1, e, 18, 19, 21), 

 lipoid corpuscles (figs. 5, e, 41) and urano-argentophile granules 

 (figs. 6, e, 29, 30), whereas argentophile granules appear to be 

 entirely absent (fig. 48). The Golgi apparatus, in the form of 

 either rings or threads (fig. 21), and pigment (figs. 22, 49) are 

 also visible in them. The cells are the largest of the islet cells 

 and are mostly of cylindrical form. The nucleus, as seen in 

 iron-hematoxylin preparations, is similar to that of the b cell. 

 It is oval in shape and usually situated at the middle of the 

 cell-body, though not rarely it is placed near an end of the cell. 

 The faintly staining nuclear network is provided with one or 

 several small nucleoli. 



It can scarcely be said that all the islet cells belong to one of 

 the five types just spoken of, as there can be found intermediate 

 forms. For example, the cell shown in figure 15 must be regarded 

 as a transitional form between the a and 6 or a and e cell. The 

 specific granules of this cell are of the same nature as those of the 

 a cell, but the nucleus has an oval form with an even contour, and 

 it has an indistinct nuclear network, just as is the case with the 

 6 or e cells. The b and e cells, on the other hand, have lipoid 

 corpuscles in common. There are cells which, like the e cells, 

 contain a large number of lipoid corpuscles, but in which specific 

 granules, though few in number, are visible. These cells must 

 be considered as intermediate between b and e cells. In fact, 



