GRAM'S METHOD. 151 



GABBETT'S METHOD for the staining of tubercle 

 bacilli recommends itself because of its simplicity and 

 the rapidity with which it can be performed. By many 

 it is considered the best method, for routine employ- 

 ment. It consists in staining the cover-slips, prepared 

 in the manner given, for from two to five minutes in 

 a cold carbol-fuchsin solution, after which they are sub- 

 jected to the action of Gabbett's methylene-blue sul- 

 phuric acid solution. This latter consists of 



Sulphuric acid, strength 25 per cent. . . 100 c.c. 

 Methylene-blue, in substance . . . . 1 to 2 grammes. 



They are then rinsed off in water and are ready for 

 examination. The tubercle bacilli will be stained red 

 by the fuchsin, while all other bacteria, cell nuclei, 

 etc., will be tinted blue. 



GRAM'S METHOD. Another differential method of 

 staining which is very commonly employed is that 

 known as Gram's method. In this method the objects 

 to be stained are treated with an aniline-water solution 

 of gentian-violet made after the formula of Koch- 

 Ehrlich. After remaining in this for twenty to thirty 

 minutes they are immersed in an iodine solution com- 

 posed of 



Iodine 1 gramme. 



Potassium iodide 2 grammes. 



Distilled water 300 c.c. 



In this they remain for about five minutes; they are 

 then transferred to alcohol and thoroughly rinsed. If 

 they are still of a violet color, they are again treated 

 with the iodine solution, followed by alcohol, and this is 

 continued until no trace of violet color is visible to the 

 naked eye. They may then be examined, or a contrast- 

 color of carmine or Bismarck-brown inay be given them. 



