INFECTIVE MILK WITHOUT UDDER DISEASE 241 



high as 55. A series of experiments were made in the laboratory 

 of the State Live Stock Sanitary Board of Pennsylvania in 1896 

 and 1897, from which it was concluded {a) that the number of 

 bacilli in the milk of tuberculous animals varies from day to 

 day ; and {U) that the tubercle bacillus may pass into the milk 

 of cows having generalised tuberculosis, but whose udders are 

 perfectly healthy so far as the most careful examination during 

 life and post-mortem could show.^ Again, Rabinowitsch and 

 Kempner inoculated the milk of fifteen cows into guinea-pigs. 

 The cows had reacted to tuberculin, but had no tuberculous disease 

 which could be detected by clinical examination, and showed 

 no sign of udder disease. The results showed that 71-4 per cent, 

 of the animals yielded milk containing virulent tubercle bacilli. 



Lastly, an elaborate series of experiments on this matter have 

 recently been conducted by J. R Mohler, of the Bureau of Animal 

 Industry at Washington. He inoculated and fed guinea-pigs upon 

 the centrifugalised sediment of milk and cream from a number of cows 

 which had reacted to tuberculin and yet revealed no clinical signs of 

 udder disease. Subsequent post-inortejn examinations of the cows 

 were made. One hundred and tvvelve cows were used, 56 of which 

 reacted to tuberculin. The combined results of the ingestion and 

 inoculation experiments show that the milk of 12 out of the 56 

 reacting cows, or 214 per cent, contained virulent tubercle bacilli. 

 Dr Mohler arrives at the following important conclusions: — (i) 

 That the tubercle bacillus may be demonstated in milk from tuber- 

 culous cows when the udders show no perceptible evidence of 

 disease either macroscopically or microscopically ; (2) that the 

 bacillus of tuberculosis may be excreted from such an udder in 

 sufficient numbers to produce infection in experimental animals, 

 both by ingestion and inoculation ; (3) that in cows suffering from 

 tuberculosis the udder may, therefore, become affected at any 

 moment ; (4) that the presence of the tubercle bacillus in the milk 

 of tuberculous cows is not constant, but varies from day to day ; 

 (5) that cows secreting virulent milk may be affected with tuber- 

 culosis to a degree that can be detected only by the tuberculin 

 test ; (6) that the physical examination or general appearance 

 of the animal cannot foretell the infectiveness of the milk ; 

 (7) that the milk of all cows which have reacted to the tuber- 

 culin test should be considered as suspicious and should be 

 subjected to sterilisation before using; and (8) that it would be 

 better still that tuberculous cows should not be used for general 

 ^ Commonwealth of Pennsylvania, Bulletin 75, pp. 66-68. 



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