TYPHOID BACILLUS 



169 



bacilli with liquid air, and then crushing them. This injected 

 into guinea pigs causes diarrhoea, mydriasis and death. 



Oxygen Requirements. It is a facultative aerobe. 



Cultural Characteristics. It grows upon all media at the tem- 

 perature of the body, 37C. and more slowly at 2oC. On gela- 

 tine plate it produces at first small colonies, yellowish and punctate, 

 which become whitish, delicately notched and ridged (Fig. 

 47). In gelatine stab culture it grows in a thread-like granular 



FIG. 47. Seventy-two hour old culture of typhoid bacillus on gelatine. 

 (Kolle and Wassermann.) 



line, without producing gas. In neither case is the gelatine lique- 

 fied. On agar plates the colonies are not so characteristic, being 

 round, grayish-white, and shining. In milk it grows well, not 

 coagulating it even after boiling, and only a very little acid is 

 produced. On acid potato the growth is characterized by its 

 invisibility, and this fact is used to differentiate it from other 

 kindred bacteria. The growth is detected only by scratching 

 with a needle. In bouillon it grows uniformly, producing very 

 little acid, and no gas. In special media (Hiss's semi-solid media) 

 thread-like colonies are produced, which are characteristic. On 

 Eisner's potato media it produces small granular, glistening 



