306 R. R. BENSLEY 



trates and stains the pancreas almost instantaneously. When a 

 sufficient depth of color has been obtained the methylene blue is 

 quickly fixed by injection of a 5 per cent solution of ammonium 

 molybdate from the pancreatic duct. If the methylene blue has 

 penetrated slowly, however, it will be found that all the dye in 

 the central portions of the pancreas has been reduced, and it will 

 be necessary in this case to expose the gland to the air before fixing, 

 in order to re-oxidise the leucobase to the blue dye. In either 

 case the preparation may be passed through alcohol to xylol 

 according to the usual Bethe method, and either examined as a 

 preparation in toto, or imbedded in paraffin and sectioned. Much 

 the best results are obtained by the total preparations, which 

 eliminate the sources of error due to the section method, but it 

 is necessary to resort to the section method for the demonstration 

 of the duct relations of those islets of Langerhans which are deeply 

 imbedded in lobules of the pancreas. In these methylene blue 

 preparations, when successful, the only structures deeply stained 

 (excluding of course the nerves) are the cells of the smaller ducts 

 and the centroacinus cells. The stain is complete, in a suitable 

 preparation every duct cell belonging to these categories being 

 stained. To use this method for the demonstration of duct rela- 

 tion to islets in the case of the free islets of the interstitial tissue 

 it is advisable to double stain with a solution containing one part 

 in 15,000 of neutral red and one in 10,000 of methylene blue. In 

 such a preparation ducts going to islets may be expected to be 

 blue while the islets themselves are red. 



3. Combination of vascular injection and vital staining for deter- 

 mining the relation of the vascular system to the islets 



The object of this method is to give an accurate delimitation 

 of the islet tissue in preparations which are injected with a colored 

 mass, for demonstrating the relations of the arteries and veins 

 to the islets. Stain the pancreas by injection from {he aorta with 

 janus green as described under method h. Allow twenty minutes 

 for reduction of the dye, then follow up with a carmine gelatine 



