112 PRINCIPLES AND PRACTICE OF MILK HYGIENE 



advanced by Theobald Smith that the offending organ- 

 isms were introduced into the udder of some of the cows 

 by infected milkers, multiplied there without producing 

 any changes in the organ or in the milk, and were elimi- 

 nated in the milk in large numbers at each milking. In 

 two of the epidemics in the United States (Chicago 

 1911, Baltimore 1912) , the milk which spread the disease 

 had been subjected to a pasteurizing process. Rosenau 

 observed that when the Streptococcus pyogenes is grown 

 in raw milk it is modified to correspond with the strepto- 

 coccus of epidemic sore throat. 



Milk from cows affected with catarrhal and paren- 

 chymatous mastitis is also objectionable because the pus 

 which it contains often gives it an unpleasant taste and 

 frequently causes it to putrefy and to curdle quickly. 

 The pus itself may be harmful to children, even if no 

 bacteria are present. The greatest harm, however, is 

 done by the bacteria. In the phlegmonous form of inter- 

 stitial mastitis the presence of fever and other constitu- 

 tional disturbances renders the milk unsuitable for food ; 

 there is also the possibility that the parenchyma of the 

 udder may at any time become affected and the causative 

 bacteria would then be eliminated in the milk. 



Therefore, when a cow is affected with mastitis, the 

 milk should not be used for food and, if possible, the cow 

 should be removed from the milk stable until the udder 

 returns to the normal condition. Cows affected with 

 infectious streptococcic, septic, or gangrenous mastitis 

 should always be isolated. When infectious streptococcic 

 mastitis is present in a herd it may be necessary to pro- 

 hibit the use of any of the milk for food unless it is 

 boiled or pasteurized, but even then such milk should 

 not be used for children. 



