458 BACTERIOLOGY. 



milk with acid reaction The colon bacillus does this 

 in from thirty-six to foi y-eight hours in the incubator. 



5. The typhoid bac Jus never causes fermentation, 

 with liberation of gas, _n media containing glucose, lac- 

 tose, or saccharose. The colon bacillus is conspicuous 

 for its power of causing gaseous fermentation in such 

 solutions. 



6. In nutrient agar-agar or gelatin containing lactose 

 and litmus tincture, and of a slightly alkaline reaction, 

 the color of the colonies of typhoid bacillus is pale blue, 

 and there is no reddening of the surrounding medium ; 

 while colonies of the colon bacillus are pink and the 

 medium round about them becomes red. 



7. The typhoid bacillus does not, as a rule, possess the 

 property of producing indol in solutions of peptone ; the 

 growth of the colon bacillus in these solutions is accom- 

 panied by the production of indol in from forty-eight 

 to seventy-two hours at 37 to 38 C. 



ANIMAL INOCULATIONS. As with the bacillus of 

 typhoid fever, the results of inoculation of animals with 

 cultures of this organism cannot be safely predicted. 

 According to the observations of Escherich, Emmerich, 

 Weisser, and others, the effects that do appear are in 

 most instances to be attributed to the toxic rather than 

 to the infective properties of the culture used. 



When introduced into the subcutaneous tissues of 

 mice it has no effect, while similar inoculations of guinea- 

 pigs are sometimes (not always) followed by abscess- 

 formation at the point of operation, or by alterations very 

 similar to those produced by intravascular inoculation, 

 viz., death in less than twenty-four hours, accompanied 

 by redness of the peritoneum and marked hypersemia 

 and ecchymoses of the small intestine, together with 



