226 GENETICS 



rather than "law." Nature no longer "selects" 

 good eyes in man by long, patient, and devious 

 processes when poor eyes are made good almost in- 

 stantly by a visit to the oculist. She has long since 

 given up providing natural weapons of defense for 

 those who have the w^its to supply themselves more 

 efficiently with artificial means of self-preservation, 

 and she no longer attempts to improve the natural 

 powers of locomotion of those who are able to tame 

 a horse to ride upon, or who build steamships, rail- 

 roads, automobiles and aeroplanes, thus accom- 

 plishing at once what would require ages at least to 

 evolve. 



Neither does the law of the survival of the fittest in 

 its original sense apply equally to man and to other 

 organisms. Human society to-day protects its unfit 

 in hospitals, asylums, and through various philan- 

 thropies, while physicians devote themselves to the 

 art of prolonging life beyond the period of usefulness. 



We do not desire these results of our modern civili- 

 zation to be otherwise, but the fact remains that some 

 of the most inflexible and universal "natural laws" 

 are ineffective in the case of man, and it is profitable 

 to bear this in mind when applying the laws of ge- 

 netics to man. 



The laboratory for human heredity is the wide 

 world, but it is obvious that the experimental method 

 which has proven so effective in studying the heredity 

 of animals and plants is impracticable in the case of 

 man. The consideration of human heredity, there- 

 fore, must always be largely from the statistical side, 



