It is generally agreed that the best method for diagnosing tuberculosis of the genito-urinary tract is by the inoculation of the urine of suspected cases into the peritoneal cavity of a guinea-pig. However, this test loses much of its practical value because of the time which must elapse before lesions are apparent in the guinea-pig after inoculation. This work has been undertaken with two purposes in view; first, to shorten the time of development of tuberculosis in guinea-pigs, so that inoculation tests will be of more practical value to the clinician; second, to determine the rôle of lymphocytes as a factor in the protection of guinea-pigs against tuberculous infection. The exposure of guinea-pigs to the roentgen ray was suggested by the favorable report of John H. Morton,1 in which it is stated that, whereas with ordinary technic a period of five weeks elapses before death, with the roentgen ray exposure