310 R. R. BENSLEY 



avoided) cleared in toluol, and mounted in balsam. This method 

 has been of exceeding value because in tissues fixed in acetic osmic 

 bichromate it permits of the differentiation of all the epithelial 

 elements of the pancreas, including their granular contents and 

 mitochondria, in a single preparation. 



d. The acid fuchsin toluidin blue method. This is the same as 

 the foregoing except that toluidin blue is substituted for methyl 

 green. 



e. The neutral gentian, acid fuchsin, picric acid, method. This 

 method has been devised to permit the study of the changes in 

 the mitochondria in a certain common form of degeneration of 

 the pancreatic cell of the guinea pig, which has been described 

 by Mankowski as a form of transition between islet cell and acinus 

 cell. It was necessary in this case to stain the mitochondrial 

 granules and the degeneration granules differentially, which was 

 accomplished as follows: 



1. Stain in neutral gentian and differentiate as indicated under 5 o. 



2. Transfer to acetone, thence to water. 



3. Fix the crystal violet stain by a solution of ammonium molybdate acting 

 for five minutes. 



4. Wash thoroughly in water, and stain in anilin acid fuchsin (method 5 c). 



5. Differentiate with a solution of picric acid in 30 per cent alcohol. 



6. Dehj^drate in absolute alcohol, clear in toluol, and mount in balsam. By 

 this method the Mankowsky granules are stained violet, the mitochondria red. 



/. The copper chrome haemaloxylin method. This method was 

 employed to stain the mitochondria in the islet cells. Sections 

 fixed in acetic osmic bichromate are prepared for staining by 

 treatment with permanganate of potassium as described above, 

 then treated as follows: 



1. Place sections for five minutes in a saturated solution copper acetate in 

 water. 



2. Wash in water and transfer to a 0.5 solution of haematoxylin in water. 



3. Wash in water and transfer to a 5 per cent aqueous solution of neutral potas- 

 sium chromate. 



4. Wash in water and differentiate in Weigcrt's borax ferricyanide solution. 



5. Wash thoroughly, dehydrate, clear, and mount in balsam. 



