CYTOLOGICAL STUDIES OF LANGERHANS's ISLETS 13 



dantly in the d cells, especially in the neighborhood of the nucleus, 

 than in the e cells (fig. 1). The mitochondrial granules are of 

 various sizes: from very small to several times the diameter of a 

 filament. They are commonly scattered throughout the cyto- 

 plasm, but frequently they are gathered together in greater or 

 less amount near one end of the cell. It is my belief that a cer- 

 tain proportion of these granules are produced by the disintegra- 

 tion of chondrioconts; in fact, it is not infrequently observed that 

 the latter carry bulbous enlargements which may become sep- 

 arated from them and increase in size (fig. 20). Some of the 

 granules are most probably of nuclear origin, as is the case with 

 a and b cells. 



Lipoid corpuscles. Many of the islet cells contain some spheri- 

 cal corpuscles of a fatty or lipoid nature, which may be designated 

 as lipoid corpuscles. These stain gray with osmic-acid solution 

 or in mixtures containing this reagent. If the piece fixed in 

 osmic acid is treated with any reducing reagent, for example, by 

 the Faure-Fremiet method, they appear as deeply stained cor- 

 puscles. The corpuscles are also found in the Weigl (figs. 38, 41) 

 and Golgi preparations, although in the latter they present a 

 shrunken, thorn-apple appearance. In the first method of Ciac- 

 cio ('11) they are stained a reddish-yellow color with sudan III 

 (fig. 5), while in the second method, they take a gray color with 

 a reddish tinge. If Ciaccio's assumption be true, these corpuscles 

 must contain neutral fat in addition to the lipoid substance. 

 They are likewise easily stained with sudan III and scarlet red 

 as applied to frozen sections. They cannot be seen in the prepa- 

 rations fixed in non-osmic mixtures and stained with alum- or 

 iron-hematoxylin, but are represented by clear vacuoles (figs. 22, 

 23) which are nothing more or less than the lipoid corpuscles 

 emptied of their contents by the dissolving effect of reagents, and 

 which, when present in abundance, give a clear, reticular, or 

 alveolar appearance to the protoplasm. Even in osmic prepa- 

 rations, it often occurs that the corpuscles are dissolved out by 

 dehydrating alcohol, and xylol, or chloroform (figs. 18, 20, 21). 



The lipoid corpuscles are characteristically spherical or drop- 

 like in shape; they vary in size, showing all grades of transition 



