248 THE CAUSATION OF DISEASE. 



to a civilized E. This E is, in such instances, by no means 

 one that is hygienically fit in every respect ; nevertheless, 

 taking the good with the bad, the white race is capable of 

 thriving in it. Many instances of extermination from this 

 cause might be cited, but it is enough to remind the reader 

 of the rapid extermination of the natives of New Zealand and 

 Australia. Seeing that all men are descendants of one com- 

 mon ancestor, it is a remarkable fact that these people should 

 be incapable of living in an E which is perfectly favourable 

 to the white race. The explanation must be sought for in 

 the fact that the growth of civilization has been gradual, and 

 man has meanwhile been adapting himself to a civilized E. 



Dr. Knox has written an interesting and elaborate work* 

 with the object of proving that each race of man is capable 

 of thriving in that particular part of the world alone in which 

 it is found, and, among many instances, he cites the case just 

 alluded to of the modern American people, who, he asserts, 

 would rapidly die out were it not for the abundant influx of 

 fresh European blood. Although I believe this position to be 

 untenable, Dr. Knox's assumption contains, nevertheless, some 

 germ of truth : it emphasizes the facts that every race has 

 become more or less perfectly adapted to its own particular- 

 region, and that, when migration to a totally different climate 

 occurs, some time is needed for re-adaptation, and it further 

 prepares us for finding that in certain cases adaptation cannot 

 occur at all. It is probable, for example, that the English 

 people could never become adapted to the Indian climate, for, 

 unless brought up among the " Hills," English children seem 

 quite incapable of growing up healthy in India. Suppose, 

 however, a colony of English people were to gradually migrate, 

 generation after generation, eastward towards the Asiatic 

 continent, and ultimately to arrive in India — then, doubtless, 

 by a gradual process, they would become more or less perfectly 

 adapted to the Indian climate. The process of adaptation, 

 would, in fact, be spread over many generations. 



* "On the Eaces of Man." 



