Environmental versus Constitutional Factors in the Development of Tuberculosis among Negroes1,2

Although tuberculosis morbidity and mortality are higher among Negroes than among whites, there is no unanimity of opinion as to whether this is due to environmental factors or to a constitutionally lower resistance of the Negro to this disease. Pinner and Kasper (1) found marked differences at autopsy in the response to tuberculosis of adult Negroes and whites, indicating a lower resistance in the Negro. The differences consisted of a greater frequency in the Negro of hematogenous and lymphogenous spread of the tuberculous disease, of massive caseation of lymph nodes, and of exudative lesions which do not respect normal anatomic boundaries of organs. Rich (2), also on the basis of autopsy findings, reports that "there is definite clinical and anatomical evidence that the Negro very commonly reacts to the 'tubercle bacillus in a manner which is different from that characteristic of the white race." The clinical and roentgenographic studies of Israel and Payne (3) bear out the necropsy studies in that they found a "group difference in the characteristics of tuberculosis among ~hites and Negroes," but they state that "anatomically typical childhood-type tuberculosis is apparently rare in white adults and infrequent in adult Negroes." These reports leave little doubt that there is a difference in the type of response of the two races to infection with tubercle bacilli. They do not however indicate the relative importance of thi~ differenc~ in the total picture of tuberculosis morbidity and mortality, nor do they offer an explanation for it. Pinner and Kasper recognize this in their warning that their study was based upon autopsy material only, and that "conclu-