320 BACTERIA PATHOGENIC IN MAN 



mineral acids and alcohol as the tubercle bacillus found in man. Many 

 of them are of the same general size and shape as the tubercle bacillus, 

 and, strangely enough, produce in animals small diseased areas which 

 not only macroscopically but also microscopically resemble miliary 

 tubercles due to the tubercle bacillus. They are, however, entirely 

 different in their culture characteristics, producing in twenty-four to 

 forty-eight hours, on ordinary culture media, moist, round colonies of 

 an eighth to a quarter of an inch in diameter, and of a more or less 

 intense pink color. In animals they produce only localized lesions, 

 causing death only when injected in large numbers. The injected 

 animals are unaffected by tuberculin injections. The chief interest 

 which these bacilli have for us is the possibility of confusing them with 

 the tubercle bacilli. This danger is always present in milk, for the grass 

 bacilli find so many means of gaining entrance to it. In the examination 

 of dust, healthy throat and nose secretions, etc., the simple micro- 

 scopic examination might lead to error. 



They can be separated from tubercle bacilli by inoculating animals 

 in which no progressive lesions will develop. If there is any doubt 

 about the nature of the infection, inject \ c.c. of tuberculin, when if 

 infected with tuberculosis they will die, but if by grass bacilli they will 

 show no reaction. Cultures from the lesions will also show, on ordinary 

 media, pink colonies if grass bacilli are present, and no growth if only 

 tubercle bacilli. 



