505 
the subject any consideration. It has been equally established that 
in advanced generalized tuberculosis the udder may secrete tubercle 
bacilli without showing any indication of being affected. Careful 
experiments performed by trained and eminently responsible inves- 
tigators have also demonstrated beyond reasonable doubt that 
tubercle bacilli at certain times may be present in the milk of cows 
affected with tuberculosis to such a degree that the disease can be 
detected only by the tuberculin test, so that in a herd of cows in 
the various stages of tuberculosis it is to be expected that some of 
them will secrete tuberculous milk, which, when mixed with other 
cows’ milk, makes the entire product dangerous. 
In this connection it may be stated that the market milk of the 
District of Columbia has recently been examined by the writer for 
the presence of tubercle bacilli bv the intra-abdominal inoculation 
of guinea pigs, and in 2 samples, or 2.7 per cent of the 73 specimens 
tested, virulent tubercle bacilli were recovered. The ease with which 
tubercle bacilli may be eliminated by the udder was strikingly illus- 
trated by an experiment conducted by the Royal British Commission, 
in which a cow injected with human tubercle bacilli under the skin 
of the shoulder began excreting tubercle bacilli from the mammary 
gland seven days later, and continued to do so until its death from 
generalized tuberculosis thirty days after inoculation. Furthermore, 
Titze, of the Ivaiserliche Gesundheitsamte, proved that human tu- 
bercle bacilli when injected into the jugular vein of milch cows may 
be excreted with the milk. In the first experiment the excretion of 
the bacilli began in the third week and continued until the 144th day. 
In a subsequent test tubercle bacilli began to be excreted after twenty- 
four hours, but no bacilli could be found after ninety-nine days. In 
both these cows only the milk from the left hind quarter proved to be 
infectious. 
It has been shown by Gaffky and Eber in Germany^ and Schroeder 
in this country that, even when the tubercle bacilli are not being 
excreted by the udder, the dust and manure of the stable where the 
diseased animals are kept are in many cases contaminated with tuber- 
cle bacilli. This contaminated material may readily infect the milk 
during the process of milking, even though the milk comes from a 
healthy cow. The importance of this method of infecting milk can 
not be too greatly emphasized when it is known that cattle in prime 
condition, without any udder lesions and with but slight alterations 
in the lungs, frequently raise tuberculous mucus into the pharynx 
while coughing, then swallow this material and thus contaminate 
the feces. In a recent examination at the Bureau of Animal Industry 
Experiment Station of the manure passed by 12 cows just purchased 
from dairy farms supplying milk to the city of Washington and 
affected with tuberculosis to an extent demonstrable only by the 
