REACTIONS OF B. TYPHOSUS AND B. COLI 325 



intestines, it is relatively and absolutely enormously increased 

 in the latter situation, where it may sometimes be almost the 

 only bacillus present. Its relations to various suppurative and 

 inflammatory conditions are described in the chapter on Suppura- 

 tion (p. 185). 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. 115). 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 twenty- 

 four hours' incubation at 

 37 C. on agar, there are 

 large superficial colonies 

 and small deep colonies 

 in the plates ; to the 

 naked eye they are 

 denser and more glisten- 

 ing than those of typhoid 

 when viewed by trans- 

 mitted 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 

 gelatin 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 gelatin 

 stab cultures a few gas bubbles sometimes develop in the 

 medium (Fig. 113, C). On potatoes in forty-eight hours there 

 is a distinct film of growth of brownish tint and moist-looking 

 surface, which rapidly spreads and becomes thicker. This con- 

 trasts very markedly with the colourless film of the b. typhosus. 

 The Comparative Culture Reactions of the B. typhosus 

 and the B. coli. The importance of the relationships between 

 the b. typhosus and the b. coli has caused great attention to be 

 paid to their biological characters, in order to facilitate the 

 distinction of the one from the other. Some of these we have 

 already noted. Of the cultural characters the growth on 



FIG. 115. Bacillus coli com munis. Film 



preparation from a young culture on agar. 



Stained with weak carbol-fuchsin. x 1000. 



