BACTERIA IN MILK 199 



elsewhere she may still excrete the bacilli in the 

 milk, but it is impossible to determine when or in 

 what numbers. The natural corollary is not to use 

 milk from a tuberculous animal. Tuberculin tests 

 are now being required almost everywhere when 

 permission to register a milch cow is asked. No cow 

 giving a tuberculin test should be used for a milk 

 supply. Bacilli are also excreted in feces of infected 

 animals, and are easily carried into the milkings by the 

 swishing tail. Tubercle bacilli of human sources may, 

 of course, be in milk if handled by a consumptive. 

 Pasteurization does not surely kill the tubercle bacillus, 

 especially if surrounded by a bit of mucus. 



Examination of Milk.- Milk is examined for the 

 presence of colon bacilli, and the whole number of bac- 

 teria just as in the case of water. For the demon- 

 stration of tubercle bacilli by stain a special technique 

 is necessary. We usually inject some of the milk, 

 cream, or sediment into guinea-pigs, and expect 

 lesions in them. The chemical examination of milk 

 usually shows its food value, which may be affected 

 by bacteria. 



