NA TURE 



641 



THURSDAY, JULY 21, 1921. 



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The Tuberculosis Problem. 



THE forthcoming international conference on 

 tuberculosis, which is to be held in London 

 on July 26-28, is likely to provide some consider- 

 able additions to our knowledge of this chief of 

 diseases, and may, it is hoped, serve also to give 

 heart to those engaged in the preventive and cura- 

 tive work which has stood the test of trial. The 

 president of the International Union against 

 Tuberculosis is the eminent French jurist and 

 statesman, M. Leon Bourgeois, and it is 

 significant of the double role of the conference 

 that Prof. A. Calmette, of Lille, will open a dis- 

 cussion on the modes of diffusion of tuberculosis 

 throughout the races of the world, while an 

 English physician. Sir H. Rolleston, will open 

 another discussion on the duty — too much 

 neglected — of the medical profession in the pre- 

 vention of tuberculosis. 



On the first subject much additional light has 

 been thrown by the investigations of Metchnikoff 

 and of Prof. Calmette himself, and by the further 

 evidence marshalled, a few months ago, in an 

 interesting contribution by Prof. Gumming, of 

 the University of Wales, to the International 

 Journal of Hygiene. In a recent volume on "The 

 Epidemiology of Pulmonary Tuberculosis," 

 Col. Bushnell, of the U.S. Army Medical 

 Service, who will take part in the London con- 

 ference, has collected a mass of evidence on the 

 racial incidence of tuberculosis, which enables us 

 to approach to a definite understanding of the 

 remarkable differences in the death-rate from 

 NO. 2699, VOL. 107] 



tuberculosis in different races. Briefly and, there- 

 fore, imperfectly summarised, the general trend 

 of facts indicates that the differences displayed 

 between different races are largely, if not entirely, 

 explicable by consideration of the age at which 

 exposure to infection by tubercle bacilli first 

 occurs, by the dosage of infection which is re- 

 ceived, and by the social and sanitary circum- 

 stances in which populations are infected. There 

 may be — and it is not improbable that there 

 are — true racial differences in susceptibility to 

 infection, due to the fact that certain races have 

 not experienced the selective effect of exposure 

 during- many generations to infection. Neverthe- 

 less, although this factor cannot be excluded by any 

 directly available evidence, it is scarcely consistent 

 with its operation on a large scale that there exist 

 remarkable differences in respect of mortality 

 from tuberculosis between persons in various 

 social strata and industrial occupations and be- 

 tween communities the members of which have 

 all been exposed for many generations to the 

 ravages of this disease. 



Whatever view is taken of the selective in- 

 fluence of exposure to tuberculosis in successive 

 generations, epidemiological facts show clearly 

 that the amount of tuberculosis in adult negroes, 

 for instance, is determined in large measure by 

 their past individual experience in respect of ex- 

 posure to the infection of this disease. In Army 

 experience, negroes who have previously lived 

 under urban conditions have had little more 

 tuberculosis than white men under similar con- 

 ditions. In the past much error has arisen from 

 not comparing white and coloured populations of 

 corresponding social status. Negroes commonly 

 live in overcrowded houses, are badly fed, and are 

 extremely dirty in their habits ; comparison should 

 therefore be between them and the occupants of 

 common lodging-houses, rather than between 

 them and the average white population. 



When, however, negroes who have previously 

 lived in remote parts where tuberculosis is not 

 prevalent are exposed to infection, they suffer to 

 an extraordinary extent. The same remarks 

 apply to Red Indians and other races having a 

 similar antecedent experience. This difference 

 between persons not exposed in early life to in- 

 fection and others who have been so exposed holds 

 good, as is well known in .^rmy experience, for 

 measles. Adults, whether coloured or white, who 

 have not previously been exposed to measles 

 suffer much more severely from this disease than 

 the average adult. In this instance, also, the 



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