CHAPTER XXVIII 

 BACTERIA OF MILK AND ITS PRODUCTS 



Introduction. Milk is one of the most important of the 

 food products. It is an excellent food for man, and it is just 

 as good food for microbes, and since milk is usually sold in its 

 raw state it happens that it frequently contains enormous 

 numbers of bacteria. Some of these bacteria produce no 

 change whatever in the milk, and their presence is a matter of 

 indifference. Certain other bacteria produce changes in the 

 milk itself, causing it to spoil. These are undesirable, al- 

 though they may in no way affect the health of the consumer. 

 Still another class of bacteria sometimes found in milk are 

 disease-producing, and against the presence of these in milk 

 the consumer should have absolute protection. 



The Bacteria in the Udder. It was formerly supposed that 

 milk in the udder of the cow was sterile, but we now know 

 that it is practically impossible, even under aseptic conditions, 

 to secure sterile milk. The number of bacteria in the milk 

 taken under the best conditions varies from two hundred to a 

 thousand bacteria per cc. 



' The Number of Bacteria in Market Milk. The number of 

 bacteria found in market milk varies greatly from a few thou- 

 sand per cc. to many million per cc. In what may be con- 

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