BACILLUS CO LI COM MUNIS. 



305 



may sometimes be almost the only bacillus present. Its 

 relations to various suppurative and inflammatory conditions 

 are described in the chapter on Suppuration (p. 157). 

 Microscopically it has the same appearances and staining 

 reaction as the typhoid bacillus, and like the latter also 

 presents variations in size, though it is usually somewhat 

 shorter (Fig. 80). It is motile, and possesses lateral flagella, 

 which, however, are fewer in number and somewhat shorter 

 than those of the 

 typhoid bacillus. It 

 is easily isolated from 

 the stools of men and 

 animals by any of the 

 ordinary methods. 

 After, e.g., twenty-four 

 hours' incubation at 

 3 7 : C. on agar, there 

 are large surface 

 colonies and smaller 

 substance colonies on 

 the plates. To the 

 naked eye they are 

 denser and more 

 glistening than those 

 of typhoid when 

 viewed by transmit- 

 ted light, and rather of a brownish-white colour. Under 

 a low objective the colonies again appear denser than 

 those of the typhoid . bacillus, and more granular. On 

 ordinary gelatine and agar media the appearances are 

 similar to those of the typhoid bacillus, but the growth is 

 whiter, thicker, and more opaque, and gives the impression 

 of having greater vigour. In the case of gelatine stab 

 cultures, a few gas bubbles sometimes develop in the 

 medium (Fig. 79, C). On potatoes in forty-eight hours there 

 is a distinct brown pellicle, with a dull surface. This con- 

 trasts very markedly with the colourless film of the B. 

 typhosus; 



20 



FIG. 80. Bacillus coli communis. Film 

 preparation from a young culture on agar. 

 Stained with weak carbol-fuchsin. x 1000. 



