TUBERCULOSIS 157 



plies, such as those represented by the supplies of the 

 larger cities, constantly contain tubercle bacilli to some ex- 

 tent. The dilution of the milk of diseased animals with 

 that of healthy animals tends to diminish the danger, both 

 to animals and to In i man beings consuming such milk. 

 The alarming extent of tuberculosis in hogs is direct evi- 

 dence of the constant and marked contamination of the 

 mixed milk. 



It is impossible to examine market milk in any effective 

 ma inier for the presence of tubercle bacilli in order to de- 

 termine whether an animal is eliminating the organisms; 

 hence, under practical conditions, it is necessary to consider 

 any animal thai has Uie disease as a potential source of 

 danger, although she may not be giving off the organisms. 

 The usual method of preventing the contamination of the 

 milk with bovine tubercle bacilli is to apply the tuberculin 

 test to the animals, and to remove all animals that react to 

 the test. 



The importance of bovine tuberculosis as a factor in the 

 occurrence of the disease in man has been established only 

 within the last few years. Through detailed studies made 

 on organisms isolated from fatal cases of the disease in 

 people of all ages, it has been possible to ascertain whether 

 the organism in question belonged to the human or the 

 bovine type. The organism from cattle is more virulent for 

 most experimental animals than is the organism from man. 

 This, together with the differences in growth on culture 

 media, enables the bacteriologist to tell whether the organ- 

 ism originally came from cattle or from man. 



From the data that have been collected in various parts 

 of the world, it is certain that bovine tuberculosis is re- 

 sponsible for a portion of this disease in man. The sus- 

 ceptibility to infection from contaminated milk is greatest 



