BACTERIUM COLI COMMUNE. 359 



It grows both with and without oxygen. 

 On gelatin. When on the surface its colonies appear 

 small, dry, irregular, flat, blue- white points that are 

 commonly somewhat denuded at the margin. They are 

 a trifle denser at the centre than at the periphery, and 

 are often marked at or near the middle by an oval or 

 round nucleus-like mass the original colony from 

 which the layer on the surface developed. When 

 located in the depths of the gelatin, and examined with 

 a low-power lens, they are at first seen to be finely gran- 

 ular and of a very pale greenish-yellow color; later 

 they become denser, darker, and much more markedly 

 granular. In shape they are round, oval, and lozenge- 

 like. When the surface colonies are viewed under a 

 low power of the microscope they present essentially 

 the same appearance as that given for the bacillus of 

 typhoid fever, viz., they resemble flattened pellicles of 

 glass-wall, or patches of finely ground colorless glass. 

 Colonies of this organism on gelatin are frequently en- 

 countered that cannot be distinguished from those result- 

 ing from the growth of the bacillus of typhoid fever, 

 though, as a rule, their growth is a little more luxu- 

 riant. 



In stab- and smear-cultures on gelatin the surface- 

 growth is flat, dry, and blue- white or pearl color. Lim- 

 ited growth occurs along the track of the needle in the 

 depths of the gelatin. As the culture becomes older, 

 the gelatin round about the surface-growth may grad- 

 ually lose its transparency and become cloudy, often 

 quite opaque. In still older cultures small root- or 

 branch-like projections from the surface-growth into the 

 gelatin are sometimes seen to occur. 



It does not cause liquefaction of gelatin. 



