TUBERCULOSIS 15 
reacting animals, which are kept for breeding purposes. The calves 
are separated from their dams immediately after birth and fed upon 
the milk of healthy cows or the sterilized milk of the reacting ones. 
This method has enabled many owners of infected animals to replenish 
their herds in from four to six years. In countries where it has been 
generally applied the percentage of tuberculous cattle has been 
wonderfully reduced. 
The conservative method, recommended by Ostertag and employed 
in Germany, consists in a repeated careful physical examination and 
the elimination of all animals exhibiting evidence of tuberculosis and 
the raising of calves on pasteurized milk or that from tuberculous 
free cows. Ostertag states that this method, if carefully carried out, 
will be effective in combating the disease and he believes will even- 
tually eradicate it. 
The method, used largely in England, of examining the milk for 
tubercle bacteria and if any are found making a careful examination 
of the herd producing it and finding the spreader of the bacteria and 
eliminating her from the dairy, was reported to have greatly reduced 
the amount of infected milk in the market. 
In the United States the method of testing the herd with tuberculin, 
slaughtering the reactors under inspection and the state paying an 
indemnity to the owner has been in operation for many years. It 
has been successful in many localities and alarge number of herds have 
been freed of the disease by this procedure. It requires, however, 
that the barns be thoroughly disinfected, the test repeated at intervals 
and only sound animals introduced. In herds where the disease has 
been of long standing it requires several years before the infection is 
entirely removed. Owners of infected herds should follow some defi- 
nite procedure, which will prevent further spread of the virus and con- 
serve the value of the animals as much as possible. Many cows are 
as valuable for beef as for milk and others, where the breeding is of 
a high quality, can be isolated under the Bang method. There seems 
to be no method of procedure that can be followed in all places. The 
principle of preventing the spread of the virus from the infected to 
the well is the only one to strictly adhere to. The application of this 
principle can be made by different methods. The method to be fol- 
lowed should be the one best adapted to the existing conditions. 
Immunization. The immunization of cattle against tuberculosis 
has been very carefully studied by a large number of investigators. 
