COLON BACILLUS 155 



phism; may grow in chains; and possesses vacuoles and polar 

 bodies at times. Is readily stained by all the common basic stains, 

 but not by Gram's method. 



Oxygen Requirements. It grows especially well in oxygen. 

 Without oxygen its growth is not so good. 



Temperature Requirements, and vital resistance. It grows well 

 at room and incubator temperature. Its thermal death-point is 

 about 62 C; light and heat are destructive to it, and its resistance 

 to antiseptics is somewhat better than that of typhoid bacillus. 



Cultures. Thrives in all common culture media, especially if 

 sugar is present. It is restrained by excess of acids produced in 



FIG. 52. Colon bacillus showing flagella. (Kolle and Wassermann.) 



culture media. On gelatine it grows like the typhoid bacillus (from 

 which it is difficult to differentiate, see page 263) in whitish raised 

 colonies that do not liquefy the media. Sometimes the growth is 

 thin and iridescent, and exhibits bizarre shapes tadpole-like and 

 lobulated. Typhoid colonies show deep furrow-like r'dges under 

 the microscope. In the special semi-solid media of Hiss, the typhoid 

 produces uniform cloudiness, with thread-like colonies. The 

 colon does not so quickly cause this cloudiness, and forms gas 



