TUBERCULOSIS, HEREDITY 

 AND ENVIRONMENT 



If we study the history of medical opinion with regard 

 to phthisis, which may readily be done in the recent 

 very able paper by Dr. Bullock and Mr. Greenwood/ 

 we find that in the past much weight has been given to 

 the constitutional factor. To the great medical writers 

 of the earlier part of last century the soil meant every- 

 thing and the germ little at all, possibly — as some of 

 their critics would now say — because they knew nothing 

 about it. With the discovery of the tubercle bacillus 

 the pendulum swung at once to the other side — the idea 

 of infection dominated everybody, and the views of the 

 clinician were replaced by those of the laboratory inves- 

 tigator, who could determine, far more dogmatically 

 than the clinician, the presence of tubercle. The result 

 was an immediate neglect both of the hereditary factor 

 and of the environmental factor. The origin of phthisis 

 was infection, and the battle against phthisis was summed 

 up in the destruction of the tubercle bacillus or of such 

 environments as were supposed to encourage its ex- 

 istence. The importance of the discovery of Koch 

 cannot be overrated, but, as a result of it, a very definite 

 line of action was taken without any adequate scientific 

 inquiry into the relative importance : 

 (i) of the hereditary factor ; 

 (ii) of the environmental factor ; 

 (iii) of the liability to infection. 



^ Royal Soc. Medicine, April, 1911. 





^'*i? 



