12 S. SAGUCHI 



fluids, sublimate-osmic-chromic acid, sublimate-osmic acid, or 

 Zenker's fluid, and staining with iron-hematoxylin or acid fuchsin. 



The specific granules present in the a, b, and c cells bear, in 

 their staining reactions, a striking resemblance to mitochondria, 

 except that they offer greater resistance to the action of acetic 

 acid. Except for these granules, there are no mitochondrial 

 filaments in these cells. If we assume that mitochondria are a 

 constant constituent of all cells', then they should also be found 

 in these three types. I am of the opinion that the specific gran- 

 ules in these cells represent mitochondria. Evidence in favor of 

 this view is: 1) the resemblance of the staining reactions of the 

 two as described above; 2) the development of the specific gran- 

 ules takes place in a manner identical to that of the mitochondria 

 in the acinus cell (Saguchi, '20); and 3) it is probable that the 

 ultimate fate of the specific granules is the same as that of the 

 mitochondria in the other types of islet cells, a question which 

 will be taken up when the lipoid corpuscles are considered. It 

 is necessary to say here a few words with regard to certain gran- 

 ules of mitochondrial nature. These are scattered sparsely 

 throughout the cytoplasm of the a and b cells (fig. l,b); they are 

 larger than the ordinary specific granules. Some of them are 

 certainly of nuclear origin, since it can often be clearly seen that 

 the nucleolus constricts off pieces which pass out of the nucleus 

 into the cytoplasm (fig. 15); some of them, however, especially 

 the smaller ones, may be formed by the growth and eventual 

 fusion of the specific granules. 



The non-granular cells, i.e., d and e cells, contain typical mito- 

 chondria in two forms — fiJamentous and granular (figs. 1, 2, 3, 7, 

 e; 18 to 21) Chondrioconts in these types of islet cells are tor- 

 . tuous, very delicate filaments which can be made out only with 

 diflficulty in the stained preparations. In the preparations 

 treated with the method of Meves or of Altmann they stain 

 very faintly, whereas in those which were fixed in osmic-subli- 

 mate mixture and stained with iron-hematoxylin, they appear 

 as relativelj^ thick, more heavily staining filaments (fig. 19). 

 They are distributed evenly throughout the cytoplasm, without 

 any local accumulation. They seem to be present more abun- 



