72 Dairy Bacteriology. 



In the case where the milk of a large number of herds 

 is mixed, this may be of some importance, but in no 

 case is it safe to assume that dilution of the milk of 

 tuberculous cows is any guarantee of safety. 



It has been shown that milk, perfectly normal in ap- 

 pearance, coming from a tuberculous udder could be 

 diluted a million times and still produce the disease on 

 inoculation into experimental animals. In the case of 

 swine, the susceptibility is so great that a single feeding 

 of infected milk, even in a very dilute condition, causes 

 with certainty the production of the disease. 



Some observers maintain that the contamination of 

 the milk with the manure of tuberculous animals is of 

 greater hygienic importance, than that coming from 

 diseased udders, since the number of animals having 

 tuberculosis of the lungs and intestines is far greater 

 than those with diseased udders. 



Economic aspects of bovine tuberculosis. Not only 

 is this disease invested with much importance because 

 of its inter-relation with the human, but from an eco- 

 nomic point of view alone, it is undoubtedly the great- 

 est scourge that affects the dairyman. Its insidiousness 

 makes it exceedingly difficult to recognize. The con- 

 sequence is that many fine herds become seriously in- 

 volved before its presence is recognized. In the main, 

 the disease is introduced into a herd by purchase, often 

 by buying in pure-bred stock to improve the quality of 

 the herd. Where the disease has been established in a 

 region for some time, there is also danger that unheated 

 factory by-products, as skim milk and whey, may func- 

 tion in its spread. "Where such conditions prevail, the 

 spread of the disease in the creamery district is ex- 

 ceedingly rapid. When once introduced into a herd, 



