32 A STUDY IN HEREDITY 



Englishmen and Polynesians, when immigrants 

 in countries where malaria, typhoid, or dysentery 

 are very rife, suffer much more than the native 

 inhabitants. When small-pox, measles, consump- 

 tion, syphilis, scarlatina, plague, or yellow fever 

 overpass their normal boundaries, and attack the 

 inhabitants of countries where they were pre- 

 viously unknown, they are destructive to a very 

 unusual degree, as in Polynesia. Vaccination has 

 been proved to be a very mild form of small-pox. 

 For centuries, and, until very recently, we were 

 scourged by small-pox ; to the Esquimaux it was 

 unknown. Most of us are able to recover even 

 from small-pox ; the Esquimaux perish even from 

 vaccinia.^ 



Clearly the different races of mankind have 

 undergone evolution against disease — this race 

 against this disease and that race against that 

 disease. In a vague way the evolution has been 

 noted by philosophically - minded medical men. 

 They have not called it evolution, but they have 

 observed that races which have been much afflicted 

 by any disease are stronger against it than races 

 that have been less, or not at all afflicted. But, 

 invariably, medical men have attributed the growth 

 of powers of resistance to the transmission of 



1 Dr William Russell, Scottish Medical and Surgical Journal, 

 April 1900, p. 330. 



