176 TYPHOID FEVER. 



with articles contaminated with typhoid fever germs has, in 

 some instances, when the animal's vitality was very much 

 lowered, produced infection, and sometimes lesions in the 

 intestines and mesenteric ganglia very much resembling those 

 found in human beings. The usual sources of infection are 

 water or milk ; in a lesser degree vegetables and fruit con- 

 taminated with human dejecta. Flies, especially the common 

 house-fly, have been found to be potent carriers of these 

 bacteria. 



Differentiation of Bacillus Typhosus from Allied 

 Groups. 



I. General Features. In many respects the Bacillus typho- 

 sus resembles very much the Bacillus coli communis, both 

 from a morphological point of view as well as in its cultural 

 peculiarities. The differentiation between the two is some- 

 times quite difficult, and it is necessary to cultivate the bacilli 

 in all the known artificial media to come to a conclusion 

 about their identity. The points of differentiation are the 

 following : 



The Bacillus coli communis is generally thicker and much 

 less motile than the typhoid bacillus. The coli communis 

 grows much more rapidly in all media. The flagella of the 

 typhoid bacillus are more numerous. The Bacillus typhosus 

 does not coagulate milk, and the coli communis does. Its 

 growth on litmus-agar remains blue, that of the coli com- 

 munis becomes red from the production of acids. The Ba- 

 cillus typhosus produces no indol, as ascertained by the ordinary 

 Dunham's test, but the coli communis produces indol very 

 rapidly. The Bacillus typhosus does not produce fermenta- 

 tion in lactose or glucose media, whereas the coli communis 

 produces fermentation and fermentative gases. On potato 

 the growth of Bacillus typhosus is almost invisible, while that 

 of Bacillus coli communis is abundant, creamy, and of a dark- 

 brown color. The serum of the blood from typhoid fever 

 cases agglutinates cultures of Bacillus typhosus. It has no 

 action on Bacillus coli communis 



