32 MANUAL OF BACTERIOLOGY. 



Bacillus of malignant edema, 



Bacillus of Friedlander, 



Bacillus proteus, 



Spirillum of Asiatic cholera, 



Spirillum of relapsing fever. 

 Staining the Bacillus of Tuberculosis. — Since the tu- 

 bercle bacillus does not take the ordinary stains readily, a very 

 large number of methods have been proposed for staining it, 

 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 

 bacillus tuberculosis is stained with great intensity, and gives 

 up its stain with difficulty. Solutions of acids will remove the 

 stain from all parts of the preparation excepting from the tubercle 

 baciUi, which retain the dye, once having acquired it. The rest 

 of the preparation may now be given a different color — con- 

 trast-stain. 



Bacilh that resist decolorization by acids are called acid-proof 

 or acid-fast. The most important are tubercle and leprosy 

 bacilh. There are various other species, however, most of 

 which are less resistant to acids and alcohol than tubercle bacilli. 

 They are discussed in the article on the bacillus tuberculosis in 

 Part IV. 



Occasionally spores of other bacteria, micrococci and homy 

 epithehal cells are imperfectly decolorized, but their forms dis- 

 tinguish them from tubercle bacilli. Minute crystaUine needles 

 which have a shape like that of bacilli are often encountered 

 in sputum, but their nature will be recognized after a little 

 practice. 



The stain for tubercle bacilli is most frequently used for 

 specimens of sputum from cases of suspected pulmonary 

 tuberculosis; it may be apphed to other fluids and secretions 

 equally well. It is not reliable, however, when apphed to 

 milk, as the oil present in milk interferes with its operation, 



