CHAPTER III 



SOURCES OF COMMON MILK BACTERIA 



Is Milk Sterile When Secreted? The first question naturally 

 arising is whether there are any bacteria in milk at the time it is 

 secreted from the cow. This question has been subject to long 

 dispute, and although many experiments have been made, there 

 is not even yet absolute agreement. It is certain that if the 

 udder of the cow is diseased, the milk may be contaminated, even 

 when secreted. It has long been known that when a cow has 

 tuberculosis in the udder her milk is practically certain to con- 

 tain tuberculosis bacilli. It is equally sure that inflamed ud- 

 ders infect the milk with bacteria. When the udder is the seat 

 of the inflammation it commonly produces pus, and this naturally 

 finds its way into the milk. With the pus there are practically 

 sure to be bacteria that are associated with the inflammatory 

 troubles. These are usually chain forming Streptococci. (Fig. 

 3, d.) Hence, the presence of large numbers of such bacteria, 

 especially if accompanied by numerous pus cells (see page 

 182), indicates a diseased condition of the udder. Such arc- 

 found in animals having mammitis or mastitis. These bacteria, 

 if in considerable numbers, are certainly detrimental to the 

 health of the persons drinking the milk. The practical con- 

 clusion is that no animal suffering from any udder affection 

 should be allowed to furnish milk for public consumption. 



Whether milk at the moment of secretion from the healthy 

 udder ever contains bacteria is not so easy to settle. Some 

 have thought that bacteria actually come from the blood of the 

 healthy cow, so that milk contains them when secreted. Others 

 have been even more positive that no bacteria come from such a 

 source, if the cow is in health. The general opinion is, however, 

 that, at least under ordinary conditions, if the cow be in health 



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