STAINS 87 



4. Bismarck brown solution. 



Water 100 c.c. 



Bismarck brown sufficient to saturate. 

 Filter and use as contrast stain. 



5. Weigert's aniline gentian violet stain. 



Gentian violet i gram. 



Dissolve in absolute alcohol 15 c.c. 



Distilled water 80 c.c. 



Then add to this 



Aniline oil 3 c.c t 



Mix, shake and filter. 

 This stain can also be prepared by taking a 



Sat. watery solution of aniline oil 100 c.c. 



Filter, then add 



Sat. alcoholic solution gentian violet 10 c.c. 



This is a very intense bacterial stain used for demonstrating 

 bacteria by the Gram method. 



Gram's method of staining. 



A cover-glass is spread with a smear of bacteria, or pus to be 

 examined. After air-drying it, and fixing it in the flame, the aniline 

 gentian violet is poured on, allowed to stand for three minutes, 

 then poured off and the preparation treated with 



Iodine crystals i gram. 



Potassium iodide 2 grams. 



Water 100 c.c. 



for two minutes. This renders the purplish preparation grayish in 

 appearance. Alcohol is now poured upon the preparation repeat- 

 edly until the alcohol does not dissolve any more color. A contrast 

 stain of Bismarck brown or dilute fuchsin is now used. If the 

 bacteria on examination remain a dark violet blue they are then 

 said to stain by Gram's method, or are "Gram positive." If they 

 are decolorized they take the contrast stain and are said not to stain 

 by this method, and are "Gram negative." 



