CHAPTER VIII 

 MILK 



BECAUSE milk is one of the most valuable articles of diet, and 

 above all because it is an indispensable food for infants and young 

 children, its purity from a bacteriological standpoint is of the great- 

 est importance. As a rule, however, it contains more bacteria 

 than any other article of food ; frequently many more than are 

 found in sewage. For the most part the bacteria which find their 

 way into milk are saprophytes, but even so, their presence in large 

 numbers is by no means desirable in a food for infants. 



When first secreted in the udder of a normal cow milk is prac- 

 tically germ free. It is impossible, however, by ordinary dairying 

 methods to obtain it in such a pure condition. Bacteria from the 

 air and surroundings find their way into the milk ducts, and as a 

 little milk always remains there from the previous milking they 

 find exactly the conditions they require : food, moisture, and a 

 suitable temperature, and they begin to multiply rapidly. By the 

 next milking they are abundant, and the first milk drawn washes 

 them into the milk pail, where they continue to grow. The milk 

 receives an additional supply from all the objects with which it 

 comes in contact. The hands of the milker, the air through which 

 it passes, and the pail into which it falls add their quota. The 

 hairs of the cow and particles of manure which may drop into the 

 pail furnish more. Generally the farmer makes an attempt to re- 

 move the coarser dirt by straining the milk through a cloth. That 

 process, however, does not affect the bacteria present. 



Even a moderate degree of cleanliness has an appreciable effect 

 upon the bacterial content. A clean barn in which to milk, clean 

 pails with small openings, clean hands, and a clean condition of the 



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