BACTERIA IN MILK 213 



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. Pasteuriza- 

 tion 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 

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

 stration of tubercle bacilli by stain a special technic 

 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. 



