MILK FROM DISEASED UDDERS. 33 



the gland is examined without the . possibility of contami- 

 nation, the inner part of the gland is free from bac- 

 teria (34) .* This fact and the possibility of occasionally 

 drawing sterile milk forces upon us the conclusion, which is 

 not disputed at the present time, that the healthy milk gland 

 does not secrete bacteria, and that the bacteria wnich com- 

 monly get into the milk, even before milking, come from the 

 exterior, making their way into the milk from the exterior 

 through the milk ducts. In short, the milk of a cow with 

 healthy udders is never contaminated by microorganisms at 

 the moment that it is secreted. 



MILK FROM DISEASED UDDERS. 



If, however, the udder is the seat of any infectious disease 

 the case may be quite different. It frequently happens that 

 the milk gland is attacked by pathogenic bacteria and be- 

 comes the seat of a variety of local infections. The gland 

 may contain centers of inflammation, a condition which indi- 

 cates the presence and multiplication of pathogenic organ- 

 isms. Mammitis and mastitis are terms used by veterinari- 

 ans as applying to certain conditions of the udder commonly 

 due to the growth of microorganisms. The tuberculosis 

 bacillus occasionally locates itself in the mammary gland and 

 produces local infection. The infection produced may, in 

 such a case, be so slight that no indication of it can be seen 

 externally and yet the mammary gland may have one or 

 more minute tubercle centers of activity. When the udder 

 is attacked by any such trouble the milk which is drawn 

 from the cow can no longer be relied upon as free from 

 bacteria. Even in these cases it is incorrect to say that the 

 cow secretes contaminated milk, but it is certainly a fact that 

 the milk at the moment of its secretion is contaminated with 

 bacteria associated with these udder diseases, so that even in 



1 Numbers inserted in the text refer to numbers in the list of 

 references that follows Chapter IX. 



3 



