CYTOLOGICAL STUDIES OF LANGERHANS's ISLETS 33 



Argentophile granules and urano-argentophile filaments seem 

 to make their appearance in this stage; their development, so 

 far as can be seen from my material, has already been mentioned 

 (figs. 25, 45, 46). Certainly, the cells with nuclei containing 

 many argentophile granules, as well as those with delicate, tor- 

 tuous urano-argentophile filaments, judging from their shape 

 and position, are nothing but acinus cells which are destined to 

 transform into islet cells. 



The Golgi apparatus of the acinus cell decreases in volume in 

 the first stage (fig. 24), and seems to disappear finally. The 

 irregularly spherical or oval corpuscles described above, which 

 show the same staining reaction as the apparatus and which 

 form a network by fusion, in all probability appear in the second 

 stage (figs. 34 to 36). How they are formed and what relation 

 they bear to other cell constituents it is impossible to determine 

 definitely, although it is certain that they are neither the remains 

 of, nor are they derived from, the Golgi apparatus of the acinus 

 cell from which the islet cell has taken origin. 



It will be seen from the foregoing that the most striking feat- 

 ures in the transformation of acinus cells into islet cells are, on the 

 one hand, the disappearance of zymogen granules, mitochondria, 

 and the Golgi apparatus characteristic of the former cells and, on 

 the other, the increase in the amount of nucleolar substance and 

 of nucleolini, followed by their passing out of the nucleus. This 

 nucleolar substance, after passing out, forms the specific granules 

 of the a and h type of cell, while the nucleolini give rise to the 

 argentophile granules. The urano-argentophile apparatus and 

 the intracellular network of the islet cell are also newly formed 

 cell-structures. The passing out of the nucleolar substance and 

 nucleolini leads to the decrease in volume of the main nucleolus — 

 a condition which is regarded as characteristic of the islet cell. 

 It must be mentioned, however, that this process is not limited 

 to the above case; I have also found (Saguchi, '20) that the mito- 

 chondrial filaments of the acinus cell are derived from the nu- 

 cleolar substance, and that nucleolini can pass out of the nucleolus 

 and eventually out of the nucleus. In the case of the islet cells, 

 the process must be regarded as being accelerated to a consid- 

 erable degree. 



