The present investigation has been undertaken with the object of obtaining information as to: (a) The relative incidence of the bovine and human types of tubercle bacillus in the infection in man. (b) The phenomena of latent tuberculous infection in a series of patients dying from causes other than tuberculosis, and in whom tuberculous lesions could be demonstrated, on naked eye examination. and (c) The question of prevalence of tuberculosis. At the same time the morphological and cultural characters of the human and bovine tubercle bacillus were observed, and the portals of entry through which tubercle bacilli may invade the human body have also received attention.