533 
Fortunately we have in the substance known as “ tuberculin ” an 
excellent agent for detecting tuberculosis in cattle when all other 
means of diagnosis fail. 
THE MANNER IN WHICH TUBERCLE BACILLI ARE EXPELLED BY 
TUBERCULOUS CATTLE. 
Examinations made at the experiment station of the United States 
Bureau of Animal Industry showed that tuberculous cows expel 
tubercle bacilli more commonly w T ith 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- 
tory acts ; and directly with their milk when their udders are affected. 
Some authorities assert that tubercle bacilli are expelled directly with 
the milk w T hen 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, 
because the tubercle bacilli it contains are numerous and of the fresh- 
est and most virulent kind. Prof. Y. A. Moore, of Cornell Univer- 
sity, says: 
It lias been shown from all examinations that have been reported of milk 
from tuberculous cows that about 15 per cent of them give oft tubercle bacilli 
with their milk during the course of the disease. The udders show tuberculosis 
in about 2 per cent of the cases. * 6 
The frequency with which the udders of tuberculous cows are 
affected is difficult to determine, as is very nicely shown by the obser- 
vations of the experiment station. For a period 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- 
culous cattle examined during the last three to four years fully 6 
per cent were found with tuberculous udders. The percentage given 
by Professor Moore is no doubt very near the truth. 
The number of tubercle bacilli expelled from the mouths and noses 
of tuberculous cattle is probably not as great as the number expelled 
under parallel conditions of disease from the mouths and noses of 
tuberculous persons, because cattle cough less frequently and less vio- 
lently and do not spit. The tubercle bacilli that are expelled with 
the feces per rectum have their origin in the lung more commonly 
than elsewhere. They are raised into the mouth and swallowed and 
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. 
6 Cornell University, Bulletin 250, January, 1908. 
