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PATHOGENIC BACTERIA. 351 



ordinary aniline dyes and by Gram's method, but they do not 



take the stains as readily as most other bacteria, and require 



somewhat longer exposure to the dye than other bacteria, on 



warming of the stain. When once stained, however, with 



aniline-water dyes or carbol-fuchsin, they are not readily de- 



colorized by acids and alcohol, which fact distinguishes them 



from all other known bacteria excepting the leprosy bacillus, 



the smegma bacillus, possibly the bacillus of syphilis (Lust- 



garten), and certain bacilli found in milk, butter and cow-dung 



and on various grasses. All of these may resist decolorization 



by acids or alcohol, and some resist 



both. They must always be kept in 



mind in making a diagnosis of tuber- ' m 



culosis. (See pages 33 and 36.) In 



examining sputum it is particularly ^ 



important to bear in mind that acid- 



proof bacilli, resembling tubercle 



bacilli, have been found in rare cases 



in gangrene of the lung. But the FIG. 91. Branching form 



of tubercle bacillus from a 



organisms found in these cases are culture. (X 1000.) 

 longer than tubercle bacilli, as a rule, 



and branch more often, besides being less resistant to decolor 

 ization.* The tubercle bacilli appear to owe their peculiar 

 staining properties to fatty substances contained in the bodies 

 of the bacilli. In stained preparations the bacillus usually 

 appears very distinctly beaded, owing to the presence of 

 stained areas which alternate with unstained areas; these 

 unstained areas have been considered by some to be spores. 



The Bacillus tuberculosis is aerobic. It requires certain 

 special media for its cultivation (see below), and it does not 

 grow so readily when it is first inoculated from tuberculous 

 material from man or lower animals as it does subsequently. 



Ophuls. Journal Medical Research. Vol. III. 1902. Ohlmacher. 

 Journal A merican Medical A ssociation. 1901. 



