236 MICRO-ORGANISMS AND DISEASE [chap. 



sufficiently well-marked differential characters, enabling us 

 to say that the typhoid bacillus is a well-defined species, 

 and to identify and distinguish it from bacillus coli and its 

 nearest allied varieties. 



The true typhoid bacillus is constantly present in the 



Fig. 83. — A Culture on the Surface of Nutrient Gelatine, obtained by 

 RUDBiNG A Particle of Spleen Pulf (Typhoid Fever) over the Sur- 

 face OF the Gelatine; showing a Confluent Mass of Colonies of 

 THE Typhoid Bacillus. 



Natural size. 



tissue of the spleen and the mesenteric glands in this 

 disease, and in this disease only ; in the spleen it occurs 

 as a rule in larger or smaller groups, though it is also found 

 here and there in small numbers and isolated ; the same 

 is the case with the mesenteric glands. In the wall of the 

 ileum, in and around the swollen or ulcerated Peyer's glands 



