382 MANUAL OF BACTERIOLOGY. 



In peptone solution it forms indol. On potato it forms an 

 abundant visible growth from cream color to pale brown. 

 Milk becomes acid and is usually, but not always, coagu- 

 lated slowly. It causes the development of gas and acid in 

 media containing dextrose or lactose. In media containing 

 neutral red the colon bacillus produces a yellow color with a 

 green fluorescence. Dififerential points between the bacillus of 

 typhoid fever and the Bacillus coli communis are as follows: 



V 



<^ .. - 



•''^ ' ^j^ -• • v' V •■ 

 - .«- \.^ ,'' L , 



Fig. 98. — Bacillus coli communis. (X 1000.) 



ist. The typhoid bacillus is actively motile; the colon 

 bacillus less actively motile. 



2d. The typhoid bacillus has numerous flagella which rise 

 from all parts of the surface; the colon bacillus has a smaller 

 number of flagella. 



3d. The colonies of the typhoid bacillus in gelatin develop 

 more slowly than those of the colon bacillus. 



4th. The superficial colonies of the typhoid bacillus on gela- 

 tin, plates are less dense than those of the colon bacillus. 



Sth. In media containing dextrose or lactose the typhoid 



