THE STAINING OF BACTERIA 101 



experience the process of decolorisatioii can be judged of >/ 

 observing the appearances under a low objective. 



THE STAINING OF BACTERIA. 



Staining Principles. To speak generally, the protoplasm of 

 bacteria reacts to stains in a manner similar to the nuclear 

 cliiomatin, though sometimes more and sometimes less actively. 

 The bacterial stains par excellence are the basic aniline dyes. 

 These dyes are more or less complicated compounds derived 

 from the coal-tar product aniline (C 6 H 5 . NH 2 ). Many of them 

 have the constitution of salts. Such compounds are divided 

 into two groups according as the staining action depends on the 

 basic or the acid portion of the molecule. Thus the acetate of 

 rosaniline derives its staining action from the rosaniline. It 

 is therefore called a basic aniline dye. On the other hand, 

 ammonium picrate owes its action to the picric acid part of the 

 molecule. It is therefore termed an acid aniline dye. These 

 t \\ groups have affinities for different parts of the .animal cell. 

 The basic stains have a special affinity for the nuclear chromatin, 

 the acid for the protoplasm and various formed elements. Thus 

 it is that the former the basic aniline dyes are especially the 

 bacterial stains. 



The number of basic aniline stains is very large. The following are 

 the most commonly used : 



i Stains. Methyl- violet, R-5R (synonyms: Hoffmann's violet, 

 dahlia). 



' ;<'iitian-violet (synonyms : benzyl-violet, Pyoktanin). 

 Crystal violet. 



Blue Stains. Methylene-blue T (synonym : phenylene-blue). 

 Victoria-blue. 

 Thionin-blue. 

 Red Stains. Basic fuchsin (synonyms : basic rubin, magenta). 



Safraiiin (synonyms : fuchsia, Girofle). 



Broivn Stain. Bismarck - brown (synonyms : vesuvin, phenylene- 

 brown). 



It is of the greatest importance that the stains used by the 

 bacteriologist should be good, and therefore it is advisable to 

 obtain those prepared by Griibler of Leipzig. 



Of the stains specified, the violets and reds are the most 

 intense in action, especially the former. It is thus easy in using 

 tin-in to overstain a specimen. Of the blues, methylene-blue 

 probably gives the best differentiation of structure, and it is 



1 This is to lie distiiiguishc'd from methyl-blue, which is a different com- 

 pound. 



