FROM THE PRACTICAL VIEWPOINT 



into the milk. Of course, if the disease existed in the 

 udder of the cow, or in the milk ducts, there would 

 then be direct contamination of the milk as it was 

 drawn. Cows more frequently, however, have the 

 disease in the lungs or other parts of the body, in 

 which case the germs will pass through the alimen- 

 tary tract and be voided with the urine and faeces. 

 If the cows are allowed to become badly soiled, 

 particles of manure and dirt, carrying with them 

 the tubercle bacilli, will inevitably fall into the 

 milk, thus infecting it. It is also possible that 

 dried manure in stables where tubercular cattle 

 are kept will produce dust, which, when stirred 

 up by the movements of the cattle or by persons 

 and by sweeping, may fall into the milk. This 

 danger is probably more imaginary than real, 

 since recent experiments by the Geneva Experi- 

 ment Station * indicate that stable dust plays a 

 part in milk infection which is of comparatively 

 little importance. It is also true that the exposure 

 of manure to light and air for a length of time 

 sufficient to produce a dry dust would tend to de- 

 stroy the tubercle bacilli. The amount of infec- 



*Bul. 409. N. Y. Ag. Exp. Sta. 

 19 



