•STAIN'S AND STAIXIXO. 289 



vesuvine, fuchsine, and Hoffman's blue. I have stained a series 

 of sections with the various nuclear dyes (for comparison), which 

 will now be projected on the screen. 



The usual process is to stain ^ or J per cent, aqueous solu- 

 tions and wash in methylated spirit. Methylene blue and methyl 

 green have the reputation of being so readily washed out in the 

 methylated spirit as to be worthless. I found that this was partly 

 true, but also that it could be obviated by washing the sections 

 (when removed from the stain) in distilled water, previous to the 

 differentiation in methylated spirit. Treated in this manner, the 

 nuclear staining is very beautiful. This alsq. applies to Hoffman's 

 blue, and partly to vesuvine ; with the latter, however, it is not a 

 necessity, Safranine and gentian violet worked better by trans- 

 ferring the sections directly from the stain into 90 p. c. alcohol. 



Contrast Stains, 



Very frequently other dyes are used to stain the ground a 

 colour which is a good contrast to that employed for the nuclei. 

 Brown, orange, or pink are used after nuclear blue or green ; 

 carmine red is generally counterstained yellow or indigo blue, and 

 fuchsine red, as in tubercle bacilli, is counterstained with nuclear 

 blue. It is important that the ground stain should be made 

 weaker than the principal stain, so that the whole tissue may be 

 shown without detracting from the nuclei or bacilli, as the case 

 may be. The following colours are used as counterstains for 

 animal ■ sections, but they are not so appropriate to vegetable 

 work : — benzopurpurine, eosine, erythrosine, orange, acid rubin, 

 and picric acid. Solutions of these are on the table. 



As examples of specific stains may be mentioned fuchsine, 

 methylene blue, and gentian violet for bacteria ; osmic acid for 

 fatty elements ; victoria blue and rose bengale for demonstrating 

 elastic fibres ; methyl violet, iodine, and safranine for amyloid 

 degeneration. 



Methylene Blue. 



This is probably the most powerful of all the aniline dyes, and 



one of the most variable in composition, as well as most erratic 



in solubility. I had hoped that the experiments, which are now 



in progress with a view to explaining these peculiarities, would 



International Journal of Microscopy and Natural Science. 



Third Series. Vol. III. u 



