124 BIOLOGY AND TECHNIQUE 



EHRLICH METHOD. 24 This method is now rarely used. Cover-slip 

 preparations are prepared as usual and fixed by heat. 



Stain with anilin water gentian-violet, hot, three to five minutes, or 

 twenty-four hours at room temperature. 



Decolorize with thirty-three per cent nitric acid one-half to one minute. 

 Treat with sixty per cent alcohol, until no color can be seen to come off. 

 Counterstain with aqueous methylene-blue. 

 Rinse in water, dry, and mount. 



ZIEHL-NEELSON METHOD. 25 Thin smears are made upon cover- 

 slips or slides. 



Fix by heat. 



Stain in carbol-fuchsin solution as given on page 115. The slide or cover- 

 slip may be flooded with the stain, and this gently heated with the flame 

 until it steams, or else the cover-slip may be inverted upon the surface of 

 the staining fluid, in a porcelain dish or watch-glass, and this heated until 

 it steams. This is continued for three to five minutes. Decolorize with 

 either five per cent nitric acid, five per cent sulphuric acid, or one per cent 

 hydrochloric acid for three to five seconds. The treatment with the acid is 

 continued until subsequent washing with water will give only a faint pink 

 color to the preparation. 



Wash with ninety per cent alcohol until no further color can be removed. 

 If, after prolonged washing with alcohol, a red color still remains in very 

 thick places upon the smear, while the thin areas appear entirely decolorized, 

 this may be disregarded. 



Wash in water and counterstain in aqueous methylene-blue for one-half 

 to one minute. 



Rinse in water, dry, and mount. 



By this method the tubercle bacilli are colored red, other bacteria and 

 cellular elements which may be present are stained blue. 



GABBET'S METHOD. 26 Gabbet has devised a rapid method in 

 which the decolorization and counterstaming are accomplished by 

 one solution. The specimen is prepared and stained with carbol- 

 fuchsin as in the preceding method. It is then immersed for one 

 minute directly in the following solution : 



Methylene-blue 2 gnis. 



Sulphuric acid 25 per cent (sp. gr. 1018) 100 c.c. 



M Ehrlich, Deut. med. Woch., 1882. 



28 Ziehl, Deut. med. Woch., 1882 Neelson, Deut. med. Woch., 1883. 



26 Goblet, Lancet, 1887. 



