INFLUENCE OF DISEASE UPON MILK 85 



cows and that these cows may eliminate virulent tubercle 

 bacilli in the fseces even when they are not infected with 

 tuberculosis. The presence of the bacilli in the faeces of 

 tuberculous cows without open lesions in the lungs or 

 intestines and without disease of the liver may be ex- 

 plained on the same basis. Titze and Jahn found that 

 in tuberculosis of the liver virulent tubercle bacilli may 

 be excreted in the bile and eliminated with the f geces, thus 

 confirming the earlier findings of Joest and Emshoff . 

 The udder and posterior parts of the cows affected with 

 open tuberculosis become soiled with the infected faeces 

 or vaginal discharges, and particles of this material drop 

 off into the milk during milking, thus infecting the milk 

 secondarily. The demonstration of tubercle bacilli in 

 the milk of individual cows does not therefore necessarily 

 indicate that the bacilli were excreted through the udder. 

 Milk from cows with open tuberculosis usually contains 

 about 1000 tubercle bacilli per c.c. While it does not 

 always produce tuberculosis when fed to guinea pigs, or 

 even when injected into them, it is often infectious and 

 must therefore be regarded as dangerous. 



(c) Cows which do not Show any Clinical Symp- 

 toms but which have Reacted to the Tuberculin Test 

 (Non-clinical Reactors). The experiments with indi- 

 vidual milk from cows which had reacted to the tuberculin 

 test, but which did not show any clinical symptoms of the 

 disease, have given contradictory results. Ostertag, 

 Brauer, Ascher, Miiller, Stenstrom, Bassett, and others 

 have found the milk from non-clinical reactors to be free 

 from tubercle bacilli, while Rabinowitch and Kempner, 

 Schroeder, Ravenel, Mohler, Martel, Guerin, DeJong, 

 Moussu, and Fay have found tubercle bacilli present in 

 milk from such cows. Ostertag tested the milk of 49 



