The increased recognition and incidence of undulant fever has fortunately been associated with new and improved methods of treating this disease, in both its acute and its chronic form. Vaccination has been employed for about ten years, in many instances with apparent success. Huddleson and Johnson1 have used a liver broth filtrate of the Brucella organism for intramuscular injection. This preparation is known as brucellin; the intramuscular injection of this filtrate has usually resulted in a local reaction and a rise in temperature. If precautions are taken to determine the sensitiveness of the patient before administration, these authors believe that it can be used without dangerous consequences. Foshay and his associates2 have employed detoxified bacterial antigens in the preparation of an antiserum for the treatment of undulant fever. Goats were used at first in the preparation of this antiserum but more recently horse serum has proved equally satisfactory.