312 MANUAL OF BACTERIOLOGY. 



3d. The colonies of the typhoid bacillus in gelatin develop 

 more slowly than those of the colon bacillus. 



4th. The superficial colonies of the typhoid bacillus on gela- 

 tin plates are less dense than those of the colon bacillus. 



5th. In media containing dextrose or lactose the typhoid 

 bacillus does not produce fermentation with gas and the colon 

 bacillus does produce gas in such media. 



6th. The tj^hoid bacillus produces an acid reaction with- 

 out coagulation in milk, and the colon bacillus produces an 

 acid reaction with coagulation. 



7th. In peptone solution the typhoid bacillus, as a rule, 

 produces no indol, and the colon bacillus produces indol. 



8th. The typhoid bacillus usually produces an invisible 

 growth on potato, the colon bacillus a visible growth. 



9th. The typhoid bacillus is said not to reduce neutral 

 red in media, and the colon bacillus to change it to a yellow 

 color. 



To these may be added the growth of the two organisms 

 on special media Hke those of Wurtz, of Eisner, of Hiss and 

 of Drigalsky and Conradi and the appHcation of the serum- 

 reaction. 



Injections of cultures of the Bacillus coli communis into ani- 

 mals produce variable and uncertain results. Subcutaneous 

 injection may lead to pus-formation ; in rabbits and guinea- 

 pigs injections may produce death apparently from poisons 

 introduced. With the blood of immunized animals a serum- 

 reaction, similar to that described for typhoid fever, may be 

 demonstrated. 



Concerning the occurrence of the Bacillus coli communis 

 in the intestine of man see page 144.* 



At autopsies on human subjects the great viscera are often 

 found to have been infected by the colon bacillus, usually when 



* See also Moore and Wright. Bacillus coli communis in the Domesticated 

 Animals. American Medicine. March 29, 1902. 



