GRAM'S METHOD OF STAINING. 33 



when treated in the way we shall describe, and if an 

 organism which presents the character of that bacillus 

 does not stain by the process it must be of some other 

 species. We shall append a table of the most impor- 

 tant pathogenic bacteria which stain and which do not 

 stain in this way. 



Requisites. i. Aniline gentian violet, or carbol-gentian 

 violet (see p. 38). 



2. Gram's iodine solution (see p. 39). 



3. Absolute alcohol or methylated spirit. 



Process. i. Spread, dry, and fix the film in the way 

 described above. Stain for two or three minutes in the 

 aniline gentian violet or carbol-gentian violet. 



2. Rinse in water to remove excess of stain and flood 

 with the iodine solution, and allow the letter to act for a 

 minute. 



3. Wash off the iodine solution with alcohol, and 

 continue the application of the latter until no more 

 colour comes away. It is best to pour a little alcohol 

 on the slide and rock the latter from side to side for a 

 minute or so, then to pour off the alcohol and add a 

 fresh supply, and continue this until the alcohol comes 

 off colourless. 



Dry and mount as before. 



The following important bacteria stain by Gram's 

 method : 



Staphylococci. 



Streptococci. 



Pneumococci. 



In fact all important pathogenic cocci except the 

 coccus of Malta fever and certain diplococci enumerated 

 below : 



The bacillus of anthrax. 

 diphtheria. 



D 



