507 
TUBERCLE BACILLI IN OTHER DAIRY PRODUCTS. 
Since milk is so often infected with tubercle bacilli, it is very evi- 
dent that food products made from milk without submitting it to 
lethal temperatures during the process of their manufacture must 
frequently harbor virulent tubercle bacilli in undesirable numbers. 
The investigations of Rabinowitsch, Klein, Laser, Bang, Petri, 
Dawson, Markl, Moller, and many others have conclusively shown 
that tubercle bacilli may be present in butter, buttermilk, margarin, 
and cheese when these products are offered for sale. Butter made in 
the customary manner and stored under the ordinary market condi- 
tions until time of sale, if dangerous through the presence of tubercle 
bacilli at the time of its manufacture, may retain its virulence through 
several months. This statement has been adequately proved by two 
series of experiments recently performed by the Bureau of Animal 
Industry. 
In one series by Mohler, Washburn, and Rogers three samples of 
butter were tested. The first was made from milk to which bovine 
tubercle bacilli had been added just before churning. They were 
obtained from a luxuriantly growing culture upon glycerin bouillon. 
Ten centigrams were removed from the surface growth of the flask, 
carefully mixed in a sterilized solution, and added to 10 gallons of 
milk. The second sample was made from milk obtained from a cow 
affected with tuberculosis of the udder. In this milk tubercle bacilli 
of extreme virulence were present in great numbers. Both the first 
and second samples of butter were salted in the usual proportions of 
1 ounce of salt to a pound of butter. The third sample was similar in 
every respect to the second, except that it was left unsalted. These 
samples of butter were tested upon guinea pigs, not only when first 
made, but also after storing for ten days in the ice chest, after hold- 
ing in cold storage for sixty days, and again after retention in cold 
storage for a period of five months (one hundred and fifty-three 
days). The results showed that each of these samples harbored viru- 
lent tubercle bacilli throughout the entire storage period, and that at 
any time they were capable of infecting guinea pigs with tuberculosis 
if injected into the peritoneal cavity, and if the tuberculous butter 
was fed to the animals generalized cases of tuberculosis were still 
capable of being developed. In these experiments 10 guinea pigs were 
fed upon each butter sample for three consecutive days and 6 were 
inoculated with the same kind of material. Six weeks later they 
were chloroformed and the visceral organs of each were carefully 
scrutinized that every trace of tuberculosis might be detected. None 
of the lots of guinea pigs remained entirely free of tuberculosis, 
although those animals which were fed upon the contaminated but- 
ter failed to contract the disease as frequently as those which were 
