366 R. R. BENSLEY 



mediate area may have few granules. Others show such a con- 

 centration of granules in one end of the cell only. Many cells 

 show the granules uniformly crowded with granules in all parts. 

 On the contrary a few cells may show no granules at all. Whether 

 these differences are due to different stages of physiological ac- 

 tivity or not, I am unable to say, for I have not been able to influ- 

 ence the number of the granules by any experimental method, 

 but the concentration in the one end of the cell is explained by 

 the fact that the fixed preparations show that this is the case in 

 the end of the cell which abuts on the capillary, while in the oppo- 

 site end of the cell the presence of the canals of Holmgren in part 

 explains the poverty in granules. 



In fresh preparations it has not been possible for me to distin- 

 guish the granules of the A cells from those of the B cells, nor 

 have I found in fresh preparations mounted with proper precau- 

 tions the differences of refractive index of the granules described 

 by Languesse. The granules of the A cells, however, hold the 

 janus green longer than those of the B cells, so that, after a time, 

 these stand out as blue stained cells on a background of red pro- 

 duced by the reduction of the janus green in the B cells. 



In proceeding to the study of the islet cells by methods of fixa- 

 tion, sectioning and staining it was necessary to secure the 

 preservation of the islet cell granules in both types of cells, and 

 to stain them differentially. Lane showed how the granules of 

 the B cell and those of the A cell could be brought out in different 

 preparations, but for experimental work it was necessary to be 

 able to identify them with certainty in the same preparation. I 

 have found that this object may be accomplished with ease in 

 preparations fixed in Lane's chrome sublimate material by stain- 

 ing in acid fuchsin after the neutral gentian. In these prepara- 

 tions the granules of the A cells are stained red, those of the B 

 cells violet. Also, in preparations fixed in acetic osmic bichro- 

 mate and stained in anilin acid fuchsin and differentiated in methyl 

 green, the A cells stain deeply red, the B cells green. Material 

 fixed in this way also stains differentially in safranin acid violet, 

 the B granules staining red the A granules violet. For demon- 

 strating the A granules alone, I have found, fixation in acetic 



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