260 THE CAUSATION OF DISEASE. 



Under such a rigorous E, the searching process of natural 

 selection is ever at work. The sickly ones who reach maturity 

 in virtue of an artificially easy E do not live on through 

 many generations. Though they survive, and though many 

 of them rear children, Nature has, so to speak, her eye upon 

 them, and sooner or later the unhealthy line is exterminated. 

 The sickly and feeble will not, in fact, be represented in remote 

 posterity ; genealogically speaking, they are on the road to 

 extinction. It is only the best physical specimens among us 

 who can enjoy the prospective honour of living through their 

 descendants in a remote posterity. These constitute the main 

 stem of the genealogical tree : from it weak and slender 

 offshoots are perpetually branching : for a few generations 

 they live on, but sooner or later they break off and decay. 



Wherefore, viewing the subject from a far-off standpoint, we 

 see that a very high physical level of health must be main- 

 tained in the case of a fortunate few ; and that the effect 

 of rendering the E less rigorous is, on the whole, rather to 

 delay the hand of Nature than to stop it. In estimating the 

 average health standard of the community, however, we must 

 include every member of it in our reckoning ; and, such being 

 the case, it is obvious that the health of the community at 

 large is lowered by rendering the E less rigorous. 



