STAINING OP PURE CULTURES. 



DEMONSTRATION II. 



StaJiiinj^ and examination of pure cultures of Bacteria 

 from li(|uid media. 



The stains which are ordinarily used are: 



(a) Gentian violet. This stain is used in several 



forms. Of these anilin water, gentian violet is most 



used. It consists of, 



Anilin oil 4 cc. 



Distiiied water 100 cc. 



Shake thoroughly, filter and add satur- 

 ated alcoholic solution of gentian 

 violet 11 cc. 



This stain ought to be freshly prepared every two or 

 three weeks. 



Gentian violet may also be used in a diluted alco- 

 holic solution, and in this form is one of the most 

 satisfactory stains for use in pure culture staining. It 

 is made at time of using by adding two or three drops 

 of filtered saturated alcoholic solution of gentian violet 

 to a watch glass of distilled water. 



{()) Methylene blue. This may be used in several 

 forms. The stain most commonly employed is Loeffler's 

 alkaline solution. Its composition is. 



Saturated alcohoiic solution of methy- 

 lene blue 30 cc. 



Tmj^ caustic potash solution . . 100 cc. 



