f 



PATHOGENIC BACTERIA. 287 



Bacillus tuberculosis. A slim bacillus 1.5 to 4 ^ in 

 length, which very frequently presents a beaded appear- 

 ance, owing to its being dotted with bright, shining spots. 

 Branching forms have been described. The tubercle bacillus 

 is considered by some to be a member of the actinomyces 

 group. It is not motile. It has not been proved that spores 

 are formed; nevertheless certain structures, like caseous 

 lymph-nodes, have been shown to be capable of infecting 

 guinea-pigs with tuberculosis, although tubercle bacilli could 



FIG. 80. 





' 



Bacillus tuberculosis, from a pure culture. (X 1000.) 



not be demonstrated in them with the microscope. This 

 makes it seem possible that the organisms were present as 

 spores which eluded the microscopical examination. The 

 tubercle bacilli stain with the ordinary aniline clyes and by 

 Gram's method. As has already been stated, when stained 

 with aniline-water dyes or carbol-fuchsin they are not 

 readily decolorized by acids and alcohol, which fact distin- 

 guishes them from all other known bacteria excepting the 

 leprosy bacillus, the bacillus of smegma, possibly the bacillus 



