Treble Staining. 41 



saturated in the first instance, and then diluted one- 

 half at least. If they are to be laid aside for some time 

 before mounting they should not be left in spirit, but in 

 oil of cloves. Only a few sections should be stained at 

 one time or some will be found much more deeply 

 stained than others. The best results will also be ob- 

 tained with material that has been hardened in chromic 

 acid. 



This staining process is well shown in a section of 

 the base of a cat or dog's tongue, cut through one of 

 the circumvallate papilla?, the section should be suffi- 

 ciently large to include some of the mucous glands, of 

 which there are a large number in that region. 



If the staining is well done it will show all the 

 muscle fibres stained with pier o- carmine, the connec- 

 tive tissue, protoplasm of cells, &c., stained with rosein ; 

 while all the nuclei in the superficial epithelium, serous 

 glands, non-striped muscle tissue in the vessels, and 

 elsewhere, are stained a brilliant green. 



The most important fact demonstrated by this pro- 

 cess is the different chemical reaction shown by the 

 various glands. In the mucous glands, while the epi- 

 thelium lining the duct is stained in precisely the same 

 manner as the superficial epithelium of the organ, it 

 will be found that the moment the secreting epithelium 

 is reached a new colour presents itself, which differs in 

 toto from either of those employed in the process ; thus 

 showing that the secretion has the power of causing 

 these two colours, green and red, to combine, forming 

 different shades from purple to blue,* according to 



* Iodine green is a very blue green. 



