f 



PATHOGENIC BACTERIA. 311 



3d. In both, spore formation is absent. 

 4th. Both are decolorized by Gram's method. 

 5th. The colonies of the typhoid bacillus in gelatin de- 

 velop more slowly than those of the colon bacillus. 



6th. The appearance of superficial colonies in gelatin 



plates. 



FIG. 89. 



Bacillus coli communis with flagella, stained by Van Ermengem's 

 method. (X 1000.) 



7th. In media containing dextrose or lactose, the typhoid 

 bacillus does not produce fermentation with gas and the 

 colon bacillus does produce gas. 



8th. The typhoid bacillus produces an acid reaction with- 

 out coagulation in milk, and the colon bacillus produces an 

 acid reaction and coagulation. 



9th. In peptone solution the typhoid bacillus, as a rule, 

 produces no indol , and the colon bacillus produces indol. 



loth. The typhoid bacillus usually produces an invisible 

 growth on potato, the colon bacillus a visible growth. 



nth. The typhoid bacillus is said not to reduce neutral 



