260 THE PRESENT EVOLUTION OF MAN — PHYSICAL 



Under such conditions, therefore, as formerly obtained 

 in the New World, the evolution of zymotic diseases of 

 the non-malarial type could hardly have occurred ; the 

 nutritive supply was insufficient, the human population 

 too scanty, to permit of saprophytic micro-organisms 

 acquiring parasitic habits in relation to man. This a 

 'priori conclusion also is amply confirmed by A posteriori 

 considerations, for no evidence is fdtthcoming to show 

 that zymotic diseases of the non-malarial type were 

 prevalent in the New World before it was infected from 

 beyond its bounds. We may read plenty of accounts 

 which set forth how Spanish, Portuguese, or English 

 adventurers suffered from " calentures," &c., but the dis- 

 eases mentioned are evidently all malarial in type. Of 

 syphilis there is indeed a tradition that it came to the 

 Old World from the New, but there is no supporting evi- 

 dence, and the tradition is negatived by the fact that 

 the disease is particularly virulent among New World 

 races, whereas it is particularly mild when attacking 

 some Old World races, such as the Portuguese. The 

 case for yelloyv fever is stronger ; and it may be in the 

 large and, at the time, somewhat densely-populated 

 West India islands this one zymotic disease of a non- 

 malarial type — perhaps it would be more correct to say 

 of a semi-malarial type — did undergo evolution, and that 

 it existed among the native Caribs before the discovery of 

 America ; but it is probable that even this disease was 

 imported from the Old World.^ "The first reliable 

 accounts of yellow fever date from the middle of the 

 seventeenth century ; they tell of the importation of 

 the disease from place to place, and from island to 

 island." It is significant that the disease prevails on 

 the West Coast of Africa, and that more than all other 



1 Hirsch's Handbook of Geographdcal and Historical Pathology, 

 vol. i. pp. 317-18. 



