508 APPLICATION OF METHODS OF BACTERIOLOGY 



2. On gelatin, colonies of the typhoid bacillus develop 

 more slowly than do those of the colon bacillus. 



3. On potato, the growth of the typhoid bacillus is usually 

 invisible (though not always); while that of the colon 

 bacillus is rapid, luxuriant, and always visible. 



4. The typhoid bacillus does not cause coagulation of 

 milk with acid reaction. The colon bacillus does this in 

 from thirty-six to forty-eight hours in the incubator. 



5. The typhoid bacillus never causes fermentation, with 

 liberation of gas, in media containing glucose, lactose, 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 accompanied 

 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 

 numerous observers 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 



