3IO MANUAL OF BACTERIOLOGY. 



than the borders, which are translucent. It usually grows 

 more rapidly in gelatin than the bacillus of typhoid fever. 

 Its growths in other media are mostly whitish. Bouillon 

 becomes clouded. Nitrates are reduced to nitrites. In 

 peptone solution it forms indol. On potato it forms an 

 abundant visible growth from cream-color to pale brown. 



FIG. 88. 



v> P* 



I* ' ~ " 



% \ * '.\ ^ ! - 



v 



* 



Bacillus coli comraunis. (X 1000.) 



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 contain- 

 ing neutral red it is stated that the colon bacillus produces a 

 yellow color with a green fluorescence. Differential points 

 between the bacillus of typhoid fever and the bacillus coli 

 communis are as follows : 



1st. The typhoid bacillus is actively motile; the colon 

 bacillus less actively, or slightly 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. 



