438 APPLIED BACTERIOLOGY 



Agar-Agar. — A dirty orange-coloured growth is slowly 

 produced. 

 Potatoes. — A deep orange growth is produced. 



Bacillus Coli Communis. — This colon bacillus, which is 

 identical with the B. Neapolitanus of Emmerich, was dis- 

 covered by Escherich in 1885, who obtained it from the 

 normal stools of children. It has since been found to be 

 widely distributed and a normal inhabitant of the intestinal 

 tract of man and animals. 



Bacillus coli is a motile, aerobic (facultative anaerobic), 

 non-sporing, non-liquefying rod. It is killed by thorough 

 dryiag, and by a temperature of 66° C. in five minutes. 

 The length of the individuals varies between 0"8 /* and 

 l"5-3 /i, though in later stages in culture both longer and 

 shorter filaments are met with; its thickness is about 

 0"4-0"5 fi. When examined in the living state from the 

 intestinal contents in health and disease, only a minority 

 of the microbes are as a rule found to be possessed of 

 motility, though in some cases motility may be observed in 

 many individuals. The same holds good for artificial 

 cultures ; as a rule, only a minority show motility, while in 

 old cultures the motile individuals are rare. 



Cultural characters of typical B. coli communis : 



Gelatine Plates. — Bacillus coli forms typical colonies on 

 the surface of gelatine at 20° C. ; after twenty-four hours 

 they are recognisable as flat, translucent, grayish, roundish 

 patches, slightly thickened in the middle part or near one 

 margin; after forty-eight hours the patches are consider- 

 ably enlarged, angular, thin and filmy, and translucent in 

 the marginal, thicker and less translucent in the middle 

 part. The whole patch is dry, whitish in reflected light, 

 and under a magnifying glass appears fairly homogeneous, 

 though after several days it commences to show some kind 



