CYTOLOGICAL STUDIES OF LANGERHANS's ISLETS 25 



show the characteristics mentioned above and the cells sketched, 

 it will be found that islet cells (for the sake of simplicity, this 

 designation is given not only to cells which constitute the typi- 

 cal islet, but also to those which occur either in small groups or 

 individually, and are to be identified with the former) are scat- 

 tered throughout the pancreas either individually or in smaller or 

 larger groups, as shown in figures 60 and 61. Whether the pre- 

 dominant occurrence of the islet cells is single or in groups seems 

 to depend upon the region from which the section is taken. 



That islet cells occur alone or in small groups among acinus 

 cells has been noted and described b^^ Laguesse ('01), TscKas- 

 sownikow ('00), Vincent and Thompson ('07), Bensley ('11-' 12), 

 and others. According to Laguesse, these cells contain safrano- 

 phile granules which are either scattered throughout the cell- 

 body or confined to the basal portion of it. Tschassownikow 

 believes these granules to be chromatophile, while Vincent and 

 Thompson say that the protoplasm of these cells gives a bathy- 

 chrome reaction. Piazza ('11), on the contrary, is of the opinion 

 that these solitary cells belong to islets, the main part of which 

 is not contained in the section under examination, for they are 

 laden with argentophile granules as is the case with cells of the 

 typical islet. On the other hand, the cells, containing minute 

 granules, which Arnold ('12) regards as a sort of acinus cell, are 

 to be identified with solitary islet cells. At least, from the 

 microchemical reactions of the granules found by him, it is prob- 

 able that they correspond to the a or h type above referred to. 



In the pancreas of the frog the solitary islet cells are met with 

 everjrwhere, not only in the center, but also near or even at the 

 periphery immediately beneath the capsule. Most of them are 

 of the h type, while cells belonging to the a type are few in num- 

 ber. I was unable, however, to determine whether or not other 

 types of solitary islet cells occur. The solitary cell (fig. 2, h) 

 is situated between the acinus cells ; at one extremity it is in con- 

 tact with the basal membrane, while the other extremity ends 

 either between the neighboring acinus cells or reaches the lumen. 

 Under these circumstances, it often occurs that the solitary cells, 

 especially those belonging to the a type, extend along the basal 



