3o8 HEREDITY AND DISEASE 



argument to say that, throughout the ages, man has been select- 

 ing the microbes, lessening their virulence, in a sense taming 

 them — sometimes to death — as his phagocytes were strengthened 

 by more suitable food, or as his " Opsonic ftidex " improved, 

 again perhaps in relation to food. As the body increases in its 

 power of holding out — and this is demonstrably modiflahle — it 

 can prolong the contest with intruding microbes with more and 

 more hope of ultimate victory. Typhus used to kill off the 

 Irish by tens of thousands, but it never seemed to leave the 

 generations less susceptible. Now, apart from an occasional 

 prowl, the typhus germ has ceased to be important, and the 

 Irish are all the stronger for its absence. 



In any case, whether microbes have been important and 

 valuable selective agents or not, it is a sad confession on the 

 part of the " paragon of animals " if he cannot discover other 

 selective agencies — more discriminating, let us hope — to take 

 the place of disease germs. 



At present, we can only indicate that the future of our race 

 depends on Eugenics (in some form or other), com.bined with 

 the simultaneous evolution of Eutechnics and Eutopias. " Brave 

 words," of course ; but surely not " Utopian " ! 



