PART Il 
BACTERIA IN DAIRY PRODUCTS 
CHAPTER XI 
BACTERIA IN MILK 
In no phase of farm life has bacteriology made such profound 
changes as in dairy methods, changes so great as to amount almost 
to a revolution. Many dairy methods of thirty years ago have 
been abandoned and many new ones adopted, chiefly through the 
discoveries of bacteriologists. 
BACTERIA IN MILK WHEN SECRETED 
Milk, when discharged into the mammary gland of a healthy 
cow, is probably free from bacteria. It may remain sterile until 
it reaches the milk duct, but often becomes contaminated while 
still in the glands themselves. The milk ducts are almost sure 
to contain bacteria, which further contaminate the milk. 
If the cow is not in perfect health even more contamination 
may occur. When a cow is suffering from generalized tubercu- 
losis, or when she has this disease localized in the udder, her milk, 
when secreted, is sure to contain bacteria. Indeed, any udder 
infection due to bacteria, even a simple inflammation of the mam- 
mary gland, is sure to result in the contamination of the milk with 
the bacteria which cause the trouble. Mulk from a cow suffering 
from udder trouble is no longer pure milk. It may contain 
tuberculosis bacillt, or, in cases of inflamed udders, it is likely 
to contain pus, together with considerable quantities of chain- 
forming streptococci. ‘These should not be present in good milk, 
and they may possibly be the cause of certain illnesses in man. 
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