PRACTICAL CONSIDERATIONS 307 



That a markedly good constitution should not be paired with 

 a markedly bad one is a second rule — a disregard of which 

 means wanton wastage. 



A third rule is that a person exhibiting a bias towards a specific 

 disease should not marry another with the same bias. A man 

 with a very marked phthisical tendency, if he marries at all, 

 should not marry a woman whose family history is known to 

 show many phthisical subjects. 



In other words, every possible care should be taken of a 

 relatively sound stock. The careless tainting of a good stock 

 is a social crime. Every reasonable precaution should be taken 

 to prevent a badly tainted stock from diffusing itself. 



(8) Besides the advance of preventive medicine, the spreading 

 enthusiasm for health, the awakening of a eugenic conscience, 

 the suggestions as to " marriage-licences " and other forms of 

 social selection, all making for the greater healthfulness of the 

 human breed, we have, of course, to remember that our race has 

 not got beyond the scope of natural selection, much as we try 

 to evade it. 



In the course of natural selection, keenest during the early 

 years of life, the most tainted and the least immune or resistent 

 tend continually to be " weeded out," and the standard of fitness 

 is thus kept from falling rapidly. When predispositions to 

 specific diseases accumulate (e.g. by in-breeding of similars), a 

 non-viable, sometimes a non-reproductive, type arises, and — 

 disappears for ever. Rotten twigs are always falling off the 

 tree of life. There is a continual irrecoverable precipitation of 

 incapables, who thus cease to muddy the stream. 



But while this is true, every one is aware that man is so con- 

 stituted that he cannot submit to Nature's winnowing. For 

 reasons that go to the very foundations of our social frame-work, 

 we can neither act as Spartan eliminators ourselves nor allow 

 Nature to have her way. That this does not prevent us from 

 being perhaps more cruel than either, is to be gravely feared, but, 



