PATHOGENIC BACTERIA. 287 



excepting the leprosy bacillus, the smegma bacillus, possibly 

 the bacillus of syphilis (Lustgarten), 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 diag- 

 nosis of tuberculosis. (See pages 33 and 294.) 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 organisms found in 

 these cases are longer than tubercle bacilli, as a rule, and 

 branch more often, besides being less 



resistant to decolorization.* The tu- 



bercle bacilli appear to owe their pecu- - ^ 



Har staining properties to fatty sub- . •<->«•■,, 



stances contained in the bodies of the '"^^ Ji\ 



bacilH. In stained preparations the ■'" 1 ' V^ 

 bacillus usually appears very distinctly ',*- _^ * 



beaded, owing to the presence of -. .''f\,V 



stained areas which alternate with un- fig. 86.— branching 



stained areas; these unstained areas ^°^^ °^ Tubercle 



Bacillus TROM A CuL- 

 have been considered by some to be tube, (x iooo.) 



spores. 



The Bacillus tuberculosis is aerobic. It is cultivated with 

 considerable difficulty — best at about 38° C. It does not grow 

 at a temperature below 29° C, and cannot therefore be cul- 

 tivated upon gelatin. It grows well upon blood-serum, where 

 the growth becomes visible in from ten to fourteen days in the 

 incubator. It forms a dry, mealy, scaly mass, elevated above 

 the surface, of a grayish-broAAm color. It also grows upon 

 glycerin-agar; or glycerin- bouillon, on which it forms a pel- 

 licle; upon potato; upon milk containing i per cent, of agar and 

 upon coagulated egg (see page 69). It is impoitantto have the 



* Ophiils. Journal Medical Research. Vol. VIII. 1902. Ohlmacher. 

 Journal American Medical Association. 1901. 



