CHAPTER XL 



Natural Selection (continued) — The Comparative Activity of the Process in 

 Civilized and Primitive Man and in the Lower Animals — The Relation 

 between the Activity of the Process and the Health of the Community. 



We have seen that natural selection is still rigorously at work 

 among men. Let us now inquire whether it is as rigorous in 

 their case as among the lower animals. 



This question is one of great moment to the pathologist, 

 for, if the process of natural elimination be checked, the health 

 standard will tend to be lowered ; I had almost written, 

 " whatsoever tends to check the process of natural elimination 

 will tend at the same time to lower the health standard," but 

 such a statement would not be altogether correct, for, by- 

 checking the spread of epidemics, for instance, we do not 

 necessarily lower the health standard, because, as we have seen, 

 the capacity of withstanding the deadly influence of a particular 

 contagion is no true measure of health or bodily vigour. A 

 sickly individual might fare better in this respect than a strong 

 and lusty one. It is, nevertheless, possibly true that, by con- 

 trolling the spread of epidemics, we have lowered the standard 

 of health, though this is by no means necessarily the case. 

 Such is the conclusion to which Orichton Browne arrives.* 

 He thinks, for instance, that nervous diseases have, in this 

 way, become more common. I am inclined, however, to receive 

 this statement with some reservation, for I can see no connec- 

 tion between the nervous diathesis and susceptibility to the 

 various contagia. 



But whatever be the truth regarding the influence of dimin- 

 ished zymotic disease on the health of the community, there can 

 be no doubt that the general diminution in mortality which 



* Vide British Medical Journal, Feb. n, 1888 : Address to the Neurological 

 Society of London. 



