INFLUENCE OF DISEASE UPON MILK 85 
cows and that these cows may eliminate virulent tubercle 
bacilli in the feeces even when they are not infected with 
tuberculosis. The presence of the bacilli in the feces 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 feces, 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 feces 
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, Stenstrém, 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, Guérin, DeJong, 
Moussu, and Fay have found tubercle bacilli present in 
milk from such cows. Ostertag tested the milk of 49 
