Reports of the Bureau of Animal Industry of the United States Department of Agriculture,1 for the fiscal year ending June 30, 1934 revealed that a total of approximately 45,500,000 hogs were killed in slaughtering establishments under the supervision of Federal meat inspectors, and that 5,102,636, or ll.l^o, of these animals, possessed lesions of tuberculosis. The disease was sufficiently extensive in more than 40,000 animals to justify condemnation of the entire carcass. In the vast majority of instances, however, tuberculosis of swine is characterized by lesions that are slight and localized, and which usually affect the lymph nodes of the head and neck, liver, and mesentery. In such animals the extent of the tuberculous infection is not sufficient to justify condemnation of the entire carcass. Instead the affected or diseased tissues are removed and the remainder of the carcass is considered suitable for human consumption. Carcasses in which the tuberculous process is too severe to warrant passing the meat unreservedly for food, but not severe enough to justify condemnation, are passed for sterilization. In 1934, 37,386 carcasses of hogs were so treated. These brief remarks on the incidence of tuberculosis in swine in the United States indicate rather clearly the prevalence of this disease among animals which contribute a considerable portion of our meat supply. While the incidence of tuberculosis among hogs in the nation as a whole is approximately 11*^, it is much higher in certain localities. In one packing establishment of which I am aware the incidence of tuberculosis in swine is strikingly high. On many occasions 15 to 25*^ of the animals killed reveal lesions of tuberculosis on postmortem examination. In most instances the disease is recognized by the occurrence of small, caseous abscesses in the substance of hyperplastic lymph nodes and it is very unusual that tuberculous lesions of a generalized character are encountered. The availability of such an abundance of material suggested the desirability of determining by experimental methods (1) if the tissues of hog carcasses which possess slighter localized lesions of tuberculosis of insufficient degree to cause condemnation or sterilization might still contain tubercle bacilli after all grossly visible evidence of the disease had been removed, and