32 TUBERCULOSIS, HEREDITY 



If, however, we accept the view that there is a 

 real retardation in the fall in the phthisis death-rate, 

 is that not precisely what we should anticipate, if we 

 attribute the change in death-rate to the natural increase 

 of immunity due to a selective death-rate acting on a com- 

 munity with varying grades of hereditary immunity ? 



Let us see if there is anything to support this view. 

 If the view be correct, we should anticipate that the fall 

 in the death-rate is largely independent of all the cru- 

 sades against tuberculosis. There are various methods 

 of carrying on the crusade against tuberculosis — the 

 supporters of individual methods believe them alone 

 to be efficient, and scoff at all others ; the leaders of 

 the medical profession state that they believe all to have 

 their proper place on occasion, which may be true but 

 does not help us very much, — and there are certain 

 doubting Thomases, who would Hke careful inquiry 

 into the efficacy of each one of them as a preliminary 

 step to real knowledge. Well — omitting our old friend, 

 cod-liver oil — there are (a) tuberculin in a variety of 

 forms and doses ; {b) the system of local visitation and 

 dispensaries ; and (c) the sanatorium ' cure '. To what 

 extent have one or all of these reduced the mortality 

 from tuberculosis, or increased the longevity of the 

 tuberculous? Well, of tuberculin I propose to say 

 nothing to-night. I have absolutely no knowledge and 

 therefore no opinion. But our Laboratory is at work 

 on the data for many thousand cases, and in another 

 twelve months it will be possible to speak more 

 definitely on the subject. Next I will take the Sana- 

 torium influence on tuberculosis. This is a very 

 thorny topic to treat towards the end of a long lecture, 

 and if I make sweeping statements w^ithout ample 

 proof, it is not absence of proof but want of time 



