533 
I Fortunately we have in the substance known as “ tuberculin ” an 
I excellent agent for detecting tuberculosis in cattle when all other 
I means of diagnosis fail. 
I THE MANNER IN WHICH TUBERCLE BACILLI ARE EXPELLED BY 
j TUBERCULOUS CATTLE. 
I Examinations made at the experiment station of the United States 
Bureau of Animal Industry showed that tuberculous cows expel 
tubercle bacilli more commonly with their feces than in other ways.® 
They also expel them with the material drooled and slobbered from 
their mouths during feeding and ruminating; with the particles of 
fluid sprayed from their mouths and noses during accelerated expira- 
j tory acts ; and directly with their milk when their udders are affected. 
I Some authorities assert that tubercle bacilli are expelled directly with 
the milk when the udder is free from disease, but the observations 
of the experiment station indicate that this does not occur unless 
cows are affected with otherwise generalized, advanced tuberculosis. 
Milk infected directly through the udder is exceedingly dangerous, 
I because the tubercle bacilli it contains are numerous and of the fresh- 
est and most virulent kind. Prof. Y. A. Moore, of Cornell Univer-- 
I sity, says : 
' It has been shown from all examinations that have been reported of milk 
from tuberculous cows that about 15 per cent of them give off tubercle bacilli 
with their milk during the course of the disease. The udders show tuberculosis 
in about 2 per cent of the cases. ^ 
The frequency with which the udders of tuberculous cows are 
I affected is difficult to determine, as is very nicely shown by the obser- 
i vations of the experiment station. For a peripd of about ten years 
only 1 per cent of the tuberculous cattle examined were found to 
|! have tuberculous udders ; while, on the other hand, among the tuber- 
I culous cattle examined during the last three to four years fully 6 
i per cent were found with tuberculous udders. The percentage given 
1 by Professor Moore is no doubt very near the truth. 
I The number of tubercle bacilli expelled from the mouths and noses 
of tuberculous cattle is probably not as great as the number expelled 
j under parallel conditions of disease from the mouths and noses of 
I* tuberculous persons, because cattle cough less frequently and less vio- 
lently and do not spit. The tubercle bacilli that are expelled with 
I the feces per rectum have their origin in the lung more commonly 
I than elsewhere. They are raised into the mouth and swallowed and 
I on their way through the intestinal tract become evenly mixed with 
the material that is ejected as feces from the bowels. The result is 
® Bureau of Animal Industry Bulletin No. 99. 
^ Cornell University, Bulletin 250, January, 1908. 
