BACTERIUM COLT COMMUNE. 325 



Its growth 011 nutrient agar-agar and on blood-serum 

 is luxuriant but not characteristic. 



In bouillon it causes diffuse clouding with sedimenta- 

 tion. In some bouillon cultures an attempt at pellicle 

 formation on the surface may be seen, but this is not 

 always the case. In old bouillon cultures the reaction 

 is seen to have become alkaline, and a decided fa3cal odor 

 may be detected, 



It produces indol in bouillon and in peptone solu- 

 tion. 



Its growth on potato is rapid and voluminous, appear- 

 ing after twenty-four to thirty-six hours in the incubator 

 as a more or less lobulated layer of a drab, dark-cream, 

 or brownish-yellow color. 



In neutral milk containing a little litmus tincture the 

 blue color is changed to red after from eighteen to 

 twenty-four hours in the incubator, and in addition, the 

 majority of cultures cause a firm coagulation of the 

 casein in about thirty-six hours, though frequently this 

 takes longer. Very rarely , the litmus may indicate the 

 production of acid and no coagulation occur. 



In media containing glucose it grows rapidly and 

 causes active fermentation with liberation of carbonic 

 acid and hydrogen. If cultivated in solid media to 

 which glucose (2 per cent.) has been added, the gas- 

 formation is recognized by the appearance of numerous 

 bubbles along and about the points of growth. If 

 cultivated in fluid media, also containing glucose, in the 

 fermentation-tube, evidence of fermentation is given by 

 the collection of gas in the closed arm of the tube. 



On lactose-litmus-agar-agar its colonies are pink and 

 the color of the surrounding medium is changed from 

 blue to red. 



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