164 BACTERIOLOGY. 



The remaining steps in the process are the same as those 

 given in the other methods. 



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. 



The cover-slips are then rinsed 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. 



PAPPENHEIM'S DECOLORIZER AND COUNTER STAIN. 

 As with the Gabbett method, the cover-slips are 

 stained for from 5 to 10 minutes in cold carbol-fuchsin. 

 They are then rinsed in water and kept in a decoloriz- 

 ing and counter-staining fluid made as follows until they 

 are of a pale blue color : 



To 100 c.c. of a saturated alcoholic solution of 

 methylene blue add 1 gram of rosolic acid and 20 c.c. 

 of glycerine. The bacilli are stained red, the balance 

 of the field blue. 



GRAM'S METHOD. Another important differential 

 method of staining which is very commonly employed 

 is that recommended by Gram. In this method the 

 objects are treated with an aniline-water solution of 

 gentian- violet made after the formula of Koch-Ehrlich. 



