BACILLUS COLI COMMUNIS 



351 



THE BACILLUS COLI COMMUNIS. 



Although the discovery of the bacillus coli communis was 

 subsequent to that of the bacillus typhosus, it is convenient to 

 commence with a description of the former, as it presents more 

 positive characters than any other member of the group to which 

 it belongs. 



Bacillus Coli Communis. Morphological Cliaracters. These 

 are best seen in cultures. The bacillus is ordinarily from 2 to 

 4 p. long and about *5 /A broad ; longer forms up to 8 or 10 /A 

 are not infrequent (Fig. 105). It is usually found to be motile, 

 but the motility varies 

 in different strains and 

 under different growth 

 conditions in the same 

 strain. Here it is best 

 to use bouillon cultures 

 incubated at 37 C. for 

 from six to twelve 

 hours. The organism 

 may stain somewhat 

 faintly with watery dyes, 

 but is readily demon- 

 strated with carbol- 

 fuchsin even in fairly 

 \\vak solution (1 of the 

 Ziehl-Neelsen stain in 

 20 of water) ; it is 

 Gram-negative. By ap- 

 propriate staining 1). coli 

 derived from cultures 



can be shown to possess fiagella springing from all round the 

 organism, varying in number and occasionally rather short. 



Culture Reactions on Ordinary Media. The following are 

 the appearances of the b. coli in the ordinary culture media : 



In bouillon, it produces a uniform turbidity. When grown in 

 fluid gelatin, it is stated by Klein to tend to form flocculi floating 

 on the surface rather than a uniform turbidity. In stab cultures 

 on jteptoue yelatin an abundant film-like growth takes place on 

 the surface, and there is a whitish or brownish-white line along 

 the stall. No liquefaction of the gelatin occurs, but occasionally 

 a few bubbles of gas develop (Fig. 109, C). In sloped cigar 

 tni>i>* a somewhat dense, glistening, white or brownish- white 

 growth occurs along the stroke. When ayar jjlates are used 



Fie. 105. Bacillus coli communis. Film 



preparation from a young culture on agar. 

 Stained with weak carbol-tuchsin. x 1000. 



