CYTOLOGICAL STUDIES OF LANGERHANS'S ISLETS 17 



argentophile granules in the cells forming the chief constituent 

 of the islet seems to point to that fact that these cells corre- 

 spond to the e type. Of the cells in which vacuoles are not evi- 

 dent, those which are laden with delicate urano-argentophile fila- 

 ments may be identified with the a cells, as the form and position 

 of the cell-bodies and the nuclei of the two are in accord. Sec- 

 ondly, the non-vacuolated, granule-containing cells, which form 

 small groups scattered throughout the acinus tissue, may be 

 regarded as corresponding to the h cells; in fact, the lipoid cor- 

 puscles of the latter are small in size and few in number, so that 

 it is difficult to make them out in the Cajal preparations. 

 Whether the narrow cells (figs. 31, 32) in the periphery of the 

 islet belong to the h type or c type is difficult to decide, although 

 the cells which contain the deeply staining protoplasm, and 

 which are interposed between the e cells, correspond in all likeli- 

 hood to d cells, for other types of cells than they are not usually 

 found between the e cells. 



That the urano-argentophile granules are formed by the dis- 

 integration of filaments has been mentioned above; but the 

 development of the filaments themselves and the ultimate fate 

 of the granules are points which have not been definitely deter- 

 mined. It not infrequently occurs that the disintegration of the 

 filaments into granules takes place near one end of the cell or 

 that the granules are especially abundant at one or both ends of 

 the cell. From these observations, it would seem that there is 

 some intimate relationship between them and blood-vessels. I 

 am of the opinion that these granules, after having undergone 

 certain modifications, pass into the blood-stream. 



Argentophile granules. In preparations fixed in formalin and 

 treated with silver nitrate, according to Cajal, there can be seen 

 in the islet, or scattered through the pancreas cells which contain 

 brown-stained granules (figs. 46, 47). Although these may be 

 designated argentophile granules, they can also be made mani- 

 fest by fixation in formalin and by staining with iron-hematoxy- 

 lin. These granules are of small size, although larger than the 

 specific granules previously spoken of. In some cases they are 

 so numerous as to fill up the cell-body, in others they are few in 

 number or located only near one end of the cell. 



