46 BACTERIOLOGY 



Of these the tubercle bacillus and the bacillus of leprosy 

 require a much longer exposure to the stain than other bacteria 

 in the list. 



Some bacteria that are not stained by Gram's method : 

 Gonococcus, 



Diplococcus intracellularis (meningitidis) , 

 Micrococcus melitensis, 

 Bacillus of chancroids (Ducrey), 

 Bacillus of dysentery (Shiga), 

 Bacillus of typhoid fever, 

 Bacillus coli, 

 Bacillus pyocyaneus, 

 Bacillus of influenza, 

 Bacillus of bubonic plague, 

 Bacillus of glanders (Bacillus mallei), 

 Bacillus proteus, 

 Spirillum of Asiatic cholera, 

 Spirillum of relapsing fever. 



Staining of Acid-proof Bacteria. A very large number of 

 methods have been proposed for staining the tubercle bacillus, 

 all of which depend upon the principle that, after adding to 

 solutions of aniline dyes certain substances, like aniline water, 

 carbolic acid, or solutions of ammonia or soda, the tubercle bacillus 

 is stained with great intensity, and gives up its stain with difficulty. 

 Solutions of acids will remove the stain from all parts of the prepa- 

 ration excepting from the tubercle bacilli, which retain the dye, 

 having once acquired it. The rest of the preparation may now 

 be given a different color contrast-stain. 



Bacilli that resist decolorization by acids are called acid-proof 

 or acid-fast. 



Some acid-proof bacteria: 

 Bact. tuberculosis, 

 Bact. leprae, 

 Bact. smegmatis, 

 Grass bacillus of Moeller, 



