308 BACTERIOLOar, 



reaction is seen to have become alkaline, and a decided 

 ecalf odor may be detected. 



It produces indol in bouillon and in peptone solution. 



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 track of the 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 its colonies are pink and the 

 color of the surrounding medium is changed from blue 

 to red. 



In Dunham's peptone solution it produces indol in 

 from forty-eight to seventy-two hours. 



It stains with the ordinary aniline dyes. It is de- 

 colorized when treated with iodine after having been 

 stained by the method of Gram. 



By comparing what has been said of the bacillus typhi 

 abdominalis and of the bacterium coli commune it will 



