AND ENVIRONMENT 43 



of the truth that one factor rather than another is at 

 the basis of the change in the prevalence of phthisis. 

 Our commission is to seek for those things which tend 

 to favour the development of a mentally and physically 

 fit race. The easy course in life is to accept what the 

 bulk of men are doing, and to praise its excellency. But 

 this Laboratory would effect Httle if it followed, rather 

 than attempted to lead, — if it failed to show cause for 

 reconsideration and for knowledge before action. In this 

 case of phthisis thousands of pounds have been spent ; 

 more thousands — indeed ^1,500,000— will be immediately 

 available, and there has been no due consideration, no 

 knowledge, before action. If, as we anticipate — if, as I 

 have endeavoured to show you to-night, the constitu- 

 tional factor is as important as, nay, is more important 

 than, the infection-factor, then from the eugenic stand- 

 point a grave responsibility rests on those who assert 

 that infection is everything, and that stocks with here- 

 ditary tuberculous diathesis have no real existence. 

 Once upon a time the medical profession told those 

 whom they suspected of a tuberculous tendency that 

 it was a good thing for themselves to marry ; then, when 

 the existence of a constitutional weakness became a 

 recognized faith, they told members of a tuberculous 

 stock that it was a bad thing for the race that they 

 should marry. Now the fashion has turned again, and 

 infection is supposed to be the sole important factor, 

 till there is danger of the tuberculous being treated as 

 pariahs and segregated. Well, now we are told that 

 those of stock in which tubercle has been rampant 

 may marry as they please, provided they sleep with 

 their bedroom windows open ! 

 Which of these opinions is right ? You may say one 



