32 * PRACTICAL BACTERIOLOGY. 



Prepare cover glass films by pressing out the particles 

 between two cover glasses, drying and fixing in the 

 flame. 



3. Staining by Ziehl-Neelsen's method. 



(a) Float the films in Ziehl's carbol-fuchsin for 5 

 to 10 minutes, keeping the stain warm. (Do not boil). 



(b) Wash off the excess of stain in water. 



(c) Rinse quickly through 33^% nitric acid. The 

 red color disappears at once. 



(d) Wash immediately in 70% alcohol for 1 to 2 

 minutes. If the red color which re-appears is persist- 

 ent, again pass the film into the acid and rinse in the 

 alcohol. , 



(e) Wash the film in water and dry. 



(/) Counterstain in Loeffler's methylene blue for ^ 

 to 1 minute. Wash in water, dry and mount as usual. 



Tubercle bacilli appear as red rods; other bacteria 

 and the nuclei of cells are stained blue. 



This method is decidedly the most accurate for 

 routine examination work. 



i. Staining by Gabbett's method. 



The same method of procedure is followed till after 

 the removal of the film from the carbol-fuchsin. It is 

 then placed for 30 seconds in Grabbett's solution: 



Methylene blue ... 2 grammes. 

 Sulphuric acid ... 25 cc. 

 Water 75 cc. 



The film is then washed in water, dried and mounted 

 in the usual manner. 



