CHAPTER XXVI 



BACTERIOLOGY OF MILK 



Milk, one of the most important articles of human 

 diet, is at the same time an excellent medium for the 

 growth and development of bacteria; hence, great im- 

 portance attaches to methods pursued at the dairy. 

 The bacteria generally found in milk have two sources — 

 they may be derived from the cow's udder, or they may 

 fall into the milk while it is being drawn, or later at any 

 stage of handling. It is practically impossible, even 

 under the very best conditions at the farm and with the 

 most approved methods of distribution, to obtain a 

 milk absolutely free from bacteria. But, fortunately, 

 the varieties generally found in market milk are not 

 pathogenic, and are not to be considered dangerous to 

 the consumer unless they are allowed to multiply abun- 

 dantly, when they cause souring and curdling or putre- 

 faction, and may thus render the milk unfit for use. 



Grading the Milk Supply. — Broadly speaking, we may 

 divide market milk into three groups: 



(a) Best quality, showing not over 10,000 bacteria 

 to the cubic centimeter. 



(h) Good quality, not over 500,000 bacteria per cubic 

 centimeter. 



(c) Poor quality, 5,000,000 to 50,000,000 and more 

 bacteria per cubic centimeter. 



In summer these normal milk bacteria multiply 

 with astonishing rapidity, and soon render the milk 



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