278 THE I'UESENT EVOI.UTFOX OF MAN — PHYSICAL 



immunity from malarial fever on the part of the negro 

 race is an accpiired, not a congenital one, as we may 

 learn by the frequent cases of sickness and death from 

 this disease among the children of the negroes in 

 Senegambia. But the same immunity is enjoyed by 

 the natives of all malarious regions, so far as concerns 

 their own home, and such other localities as are affected 

 by malaria less severely than it ; so that one might 

 almost formulate a general rule that the predisposition 

 to malarial sickness becomes weaker in proportion as 

 the individual has been continuously exposed, from 

 birth to maturity, to more or less severe malarial influ- 

 ences, without suffering from them to any considerable 

 extent." — Hirsch, Cfcographical and Historical PatJiologi), 

 vol. i. pp. 243-4. 



The passage last quoted furnishes an example of 

 facts which may be accepted, but inferences which must 

 be disputed. The sweeping generalization, that the 

 " relative immunity from malarial fever on the part of 

 the negro race is an acquired, not a congenital one," 

 cannot be accepted as correct. Were it so, it would be 

 as easy to rear European children in malarious countries 

 as it is to rear the children of natives, and under equally 

 insanitary conditions; whereas the fact is, that even 

 under the best conditions procurable, it is difficult to rear 

 European families in such countries as India, and 

 practically impossible to do so in such countries as 

 Senegambia. Moreover, characters which appear late 

 in the ontogeny are not necessarily acquired. The 

 superior immunity or much of it exhibited by adult 

 negroes may be, and probably is, as truly congenital as 

 are their permanent teeth or their beards. That some 

 increase of resisting power may be acquired against 

 malaria by continual residence in its presence is 

 rendered certain by the fact, that natives of countries 

 infested by it exhibit greater susceptibility when 



