Attempts to control any infectious disease are aimed at eliminating either the source of infection or the means of its transmission, or at altering the susceptibility of the host to the disease. Since in the treatment of bovine tuberculosis it has not been found practicable to alter the susceptibility of the animal by immunization, or to prevent transmission of the disease by isolating infected cattle, the disease has been attacked by removing the source of the infection. This consists of applying the tuberculin test and destroying all cattle that exhibit hypersensitivity to tuberculin.