84 MICROSCOPICAL EXAMINATION OF BACTERIA 



(d) Thionin blue. 



(e) Bismarck brown. 



(f) Neutral red. 

 (B) Acid: 



(a) Eosin, aqueous yellowish. 



(b) Safranine. 



These dyes are kept in i per cent, aqueous solution 

 to which is added 5 per cent, of alcohol, as a preserva- 

 tive. They are generally used in this form. 



A few nuclear stains (carmine, haematoxylin) are 

 occasionally used more especially in ''section" work. 



Decolour isation. After overstaining, films may be 

 decolourised by washing for a longer or shorter time 

 in one of the following reagents arranged in ascending 

 order of power 



1. Water. 



2. Chloroform. 



3. Acetic acid, i per cent. 



4. Alcohol. 



5. Alcohol absolute, } 



Acetic acid, i per cent., J e< l ual P arts - 



Hydrochloric, i per cent, aqueous 



solution. 

 Hydrochloric, i per cent, alco- 



s TV/,-. 1 . -, holic (oo per cent.) solution. 



6. Mineral acids : _ . , y 



Sulphunc, 25 per cent, aqueous 



solution. 



Nitric, 33 per cent, aqueous solu- 

 tion. 



Counter staining. Use colours which will contrast 

 with the first stain; e. g., 

 Vesuvin, 



for films stained by methylene-blue or 

 Gram's method. 



Neutral red, 



Eosin, 



Fuchsin, 



Methylene-blue, I , 



^ , . . t } for films stained by fuchsm. 



Gentian violet, J 



