Staining 353 



is counterstained in a dilute aqueous solution of Bismarck 

 brown or vesuvin, the excess of stain washed off in water, 

 and the specimen dried and mounted in balsam. The 

 tubercle bacilli are colored a fine dark blue, while the pus- 

 corpuscles, epithelial cells, and other bacteria, having been 

 decolorized by the acid, will appear brown. 



This method, requiring twenty-four hours for its com- 

 pletion, has fallen into disuse, as it is desirable to know in 

 the briefest possible time whether bacilli are present in the 

 sputum or not. 



/ Ziehls Method. Among clinicians, Ziehl's method of 

 /staining with carbol-fuchsin has met with just favor. It is 

 ^as follows: After having been spread, dried, and fixed, 

 the cover-glass is held in the bite of an appropriate forceps 

 (cover-glass forceps), or the slide spread at one end is held 

 by the other end as a handle, and the stain (fuchsin, i ; 

 alcohol, 10 ; 5 per cent, phenol in water, 100) dropped upon 

 it from a pipet. As soon as the entire smear is covered 

 with stain, it is held over the flame of a spirit lamp or 

 Bunsen burner until the stain begins to volatilize a little. 

 When vapor is observed, the heating is sufficient, and the 

 temperature can be maintained by intermittent heating. 



If evaporation take place, a ring of incrusted stain at the 

 edge prevents the prompt action of the acid. To prevent 

 this, more stain should now and then be added. The stain- 

 ing is complete in from three to five minutes, after which 

 the specimen is washed off with water, and then with a 3 

 per cent, solution of hydrochloric acid in 70 per cent, alco- 

 hol, 25 per cent, aqueous sulphuric, or 33 per cent, aqueous 

 nitric acid solution dropped upon it for thirty seconds, or 

 until the red color is just extinguished. The acid is care- 

 fully washed off with water, the specimen dried and mounted 

 in Canada balsam. Nothing will be colored except the 

 tubercle bacilli, which appear red. 



Gobbet's Method. Gabbet modified the method by 

 adding a little methylene-blue to the acid solution, which 

 he makes according to this formula: 



Methylene-blue 2 



Sulphuric acid 25 



Water 75 



In Gabbet's method, after staining with carbol-fuchsin 

 the specimen is washed with water, acted upon by the 

 23 



