KILLED, STAINED 83 



If the film has been prepared from blood or blood- 

 stained fluid, treat with acetic acid 2 per cent, for two 

 minutes after fixation. Wash with water, dry, and 

 proceed with the staining. (This will remove the 

 haemoglobin and facilitate examination.) 



Staining. 



1. Rest the cover-slip, film side uppermost, on the 

 rubber mat. 



2. By means of a drop-bottle, cover the film side of 

 the cover-slip with the selected stain, allow it to act 

 for a few minutes, then wash off the excess in running 

 water. 



The penetrating power of stains is increased by (a) 

 physical means e. g., heating the stain; (6) chemical 

 means e. g., by the additon of carbolic acid, 5 per 

 cent, aqueous solution; caustic alkalies, 2 per cent, 

 aqueous solutions; water saturated with aniline oil; 

 borax, 0.5 per cent, aqueous solution. 



The most commonly used dyes for cover-slip film 

 preparations are the aniline dyes. 

 (A) Basic: 



(a) Methylene-blue. 



(b) Gentian violet. 



(c) Fuchsin. 



These dyes are kept in saturated alcoholic (90 per 

 cent.) solutions so that decomposition may be retarded. 



Two or three drops of alcoholic solution of these 

 dyes to, say, 4 c.c. water, usually makes a sufficiently 

 strong staining fluid for cover-slip film preparations. 



Carbolic methylene-blue (C.M.B.) and carbol fuchsin 

 (C.F.) are prepared by covering the cover-slip with 5 

 per cent, solution of carbolic acid and adding a few 

 drops of the saturated alcoholic solution of methylene- 

 blue or fuchsin respectively to it. For aniline gentian 

 violet (A.G.V.) the stain is added to a saturated solu- 

 tion of aniline oil in water. 



