THE STAINING OF BACTERIA. 47 



4. Ziehl's Carbol-fuchsin Method. 

 Make a solution of carbol-fuchsin as follows : 



Fuchsin, 1 part; 



Crystallized carbolic acid, 5 parts ; 



Alcohol, 10 " j 



Water, 100 " . 



Immerse the glass in or cover same with the carbol-fuchsin 

 solution, heat gently over the flame of a Bunsen burner, gradu- 

 ally bringing to a point just below boiling; repeat this two 

 or three times ; after which immerse in nitric acid solution 

 (1 part of acid to 3 parts of water) until the color is scarcely 

 visible to the naked eye. To ascertain this, wash off the acid 

 from the film with water. If color is still faintly visible, 

 remove it by dipping into alcohol ; wash in water, dry, 

 mount in Canada balsam, and examine. A contrast-color 

 may be given to the rest of the specimen by employing 

 methylene-blue. 



This is a useful method in coloring cover-glass preparations 

 for tubercle bacilli or for the Bacillus leprae. 



5. Gabbett's Method. 



This is a modification of Ziehl's method, and is perhaps the 

 best method, on account of its simplicity and rapidity, for the 

 staining of the tubercle bacillus in secretions. It is as fol- 

 lows : Prepare a slide or cover-glass film as indicated, im- 

 merse in Ziehl's carbol-fuchsin solution for ten minutes, remove 

 to Gabbett's sulphuric acid methylene-blue solution for three 

 to five minutes, rinse in water, dry, mount, examine. The 

 tubercle bacilli are colored red and the other bacteria and cell- 

 nuclei are colored blue. 



Gabbett's solution consists of : 



Methylene-blue, 1 to 2 parts; 



Sulphuric acid, 25 " ; 



Water, 75 " . 



