BACILLUS COLI COMMUNIS. 325 



water have usually been found to be dead after three weeks 

 (Frankland). 



The Bacillus coli communis. This bacillus is the chief 

 organism present in the small intestine in normal conditions, 

 and, with many other bacteria, it also inhabits the large intes- 

 tine. During typhoid fever, and other pathological conditions 

 affecting the 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 suppu- 

 rative and inflammatory conditions are described in the chapter 

 on Suppuration (p. 196). Microscopically it has the same appear- 

 ances and staining reaction as the typhoid bacillus, and like the 

 latter also presents variations in size, though it is usually some- 

 what shorter (Fig. 118). It is usually sluggishly motile, but 

 occasionally motility seems to be quite absent, and it possesses 

 lateral flagella, which, however, are fewer in number and some- 

 what shorter than those of the typhoid bacillus. It is easily 

 isolated from the stools of men and animals by any of the ordi- 

 nary methods. After, e.g. 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 glistening 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 impres- FIG. n8. Bacillus coli communis. Film 

 Sion Of having greater vigour. Preparation from a young culture on agar. 



Stained with weak carbol-fuchsin. X loco. 



In the case of gelatin stab- 

 cultures a few gas bubbles sometimes develop in the medium 

 (Fig. 1 1 6, C) due to presence of muscle sugar in the beef infusion. 

 On potatoes in forty-eight hours there is a distinct film of growth 

 of brownish tint and moist-looking surface, which rapidly spreads 



