Infection of Milk. 63 



The organism must live a parasitic life in the animal, 

 developing- in the udder, and so infect the udder. It 

 may, of course, happen that diseases toward which do- 

 mestic animals alone are susceptible may be spread 

 from one animal to another in this way without affect- 

 ing human beings. 



In the second group the bacterial species live a sapro- 

 phytic existence, growing in milk, as in any other nu- 

 trient medium, if it happens to find its way therein. In 

 such cases, milk indirectly serves as an agent in the dis- 

 semination of .disease, by giving conditions favorable 

 to the growth of the disease germ. 



By far the most important of diseases that may be 

 transmitted directly from animal to man through a 

 milk supply is tuberculosis, but in addition to this, foot 

 and mouth disease (aphthous fever in children), Malta 

 fever, and acute enteric troubles have also been traced 

 to a similar source of infection. 



The most important specific diseases that are dissem- 

 inated through subsequent infection of the milk are 

 typhoid fever, diphtheria, scarlet fever, and cholera, 

 but, of course, the possibility exists that any disease 

 germ capable of living and thriving in milk may be 

 spread in this way. In addition, to these diseases that 

 are caused by the introduction of specific organisms 

 (the causal organism of scarlet fever has not yet been 

 definitely determined), there are a large number of 

 more or less illy defined troubles of an intestinal char- 

 acter that occur especially in infants and young chil- 

 dren that are undoubtedly attributable to the activity 

 of micro-organisms that gain access to milk during and 

 subsequent to the milking, and which produce changes 



