508 
injected. This experiment is to be extended further in order to de- 
termine the maximum time in which infected butter, both salted and 
unsalted, will remain virulent when kept in cold storage under nor- 
mal trade conditions. As the temperature in the cold-storage rooms 
is very low, the evidence shows that the tubercle bacilli are held un- 
changed in the frozen butter for a long period, but that they slowly 
lose their vitality. 
In another series of experiments by Schroeder and Cotton, of the 
Bureau Experiment Station, butter was made from the milk of a cow 
affected with udder tuberculosis. After salting at the rate of 1 ounce 
of salt to a pound of butter, the butter was kept without ice in a cellar 
in which the temperature remained fairly constant at 60° F., and 
from time to time, up to one hundred and sixty days from the making 
of the butter, guinea pigs were inoculated with portions of the 
butter. More than 60 guinea pigs were thus inoculated and, with 
the exception of 5 that died prematurely and 1 that was killed, all 
died of generalized tuberculosis, and the one that was killed was also 
found affected. 
In cheese also tubercle bacilli may become mixed up with the curd 
during the process of manufacture, and they have been shown to re- 
main virulent for over three months. As a result of Galtier’s experi- 
ments conducted with cheese, both salted and not salted, which was 
found to contain tubercle bacilli when two months and ten days old 
he concluded that coagulated milk, fresh cheese, and salted cheese 
made from the milk of tuberculous cows may infect man, and that the 
by-products fed to swine and chickens may infect these animals. In 
experiments made in Switzerland to determine the fate of tubercle 
bacilli in cheese it was demonstrated that they died between the 
thirty-third and fortieth day in cheese made after the Em-mental 
method, but considerably later in cheese made approximately after 
the Cheddar method. An emulsion of tubercle bacilli was added to 
milk at the same time as the rennet, and cheese was made from the 
milk in the manner required to obtain Cheddar cheese. From the 
time of manufacture average samples of the cheese were taken weekly, 
macerated in sterile water, and filtered. Guinea pigs were inoculated 
with portions of the filtrate, and it was found that the germinating 
power of the tubercle bacilli lasted one hundred and four days, but 
after one hundred and eleven days they were incapable of conveying 
the disease to guinea pigs by inoculation. Harrison concluded that 
these experiments justif} T the statement that Emmental cheese may 
be eaten with safety, as the period of ripening is much longer than the 
period during which the bacilli become inocuous. Cheddar cheese, 
he states, is seldom eaten under four months from time of manufac- 
ture, and during this period the tubercle bacilli lose their vitality. 
Notwithstanding this, however, the writer recommended the pas- 
