278 EPIDEMIC AND ENDEMIC DISEASE 



legend, we seem to gleam dim accounts of air-borne pestilences. 

 Thus the disaster which befell the Assyrian host before Jerusalem 

 and that which afflicted the Greeks before Troy had that appalling 

 suddenness which characterizes an air-borne epidemic occurring in 

 a population entirely susceptible. 



461. To sum up, human microbic diseases seem to have origi- 

 nated in the Eastern Hemisphere, which has long been thickly 

 populated, each disease from a single centre, whence it spread 

 facts which appear to be confirmed by the apparently total lack of 

 all microbic diseases, except malaria, in the various parts of the 

 West before the invasion by Europeans and their subsequent 

 establishment there. Earth-borne and contagious diseases must 

 have been endemic from their origins, as also must have been some 

 insect-borne maladies. Doubtless water-borne diseases early 

 became endemic wherever the conditions, including a dense and 

 settled human population, were favourable. Air-borne disease was 

 probably epidemic at first, passing with great rapidity and fear- 

 ful results from one region to another, but gradually became 

 endemic in all thickly populated localities that were in frequent 

 communication with surrounding areas. There can be no doubt 

 that all our familiar maladies were rife in Europe at the time when 

 Columbus set out on his fateful voyage, and initiated the greatest 

 tragedy, the most tremendous event in human history. 



462. On the one side of the Atlantic were peoples who for 

 thousands or tens of thousands of years had been slowly evolving 

 resisting power against a multitude of maladies peoples whose 

 increase had been very slow, largely because of the numbers of the 

 unfit that had perished from disease, maladies that had gradually 

 passed from the epidemic form in which the selection of their 

 victims was haphazard and imperfect, to the endemic form, when 

 selection was more thorough and clean. These Eastern peoples 

 now dwelt under conditions that would have been fatal to their 

 remote ancestors. Their civilization, with its dense communities 

 and constant communication between distant parts, was absolutely 

 conditioned by their power to resist many diseases. Their houses, 

 especially in their great cities, were dark, ill-ventilated, and 

 crowded both with men and microbes. Their clothes, which their 

 climate necessitated and custom and religion ordained even in 

 warmer regions, were vehicles almost ideally adapted for the con- 

 veyance of disease. On the other side of the Atlantic were peoples 

 who had undergone no evolution against any zymotic malady except 

 malaria, and against the latter only in the wooded tropical parts. 



