498 



ZOOLOGY 



Epidemic 



Racial sus- 

 ceptibmty 



hearts and keen minds which wrought weal out of the 

 very elements of woe. 



io. It would be quite erroneous to emphasize epi- 

 demies and military struggles alone, forgetting the 

 tremendous significance of endemic disease and of 

 economic forces in society. These slower processes are 

 hard to grasp, because they are only imperfectly or not 

 at all known to those who are affected by them;' the 

 "original sources," the contemporary chronicles, are 

 silent concerning them. Thus there seems to be reason 

 for thinking that the Golden Age of Greece passed 

 away, never to return, not so much on account of wars 

 and invasions, as because of the selective action of 

 malaria. Conquests had brought to the Grecian shores 

 captives of dusky hue, contrasting with the fair folk 

 of aristocratic Greece. The malaria organism, existing 

 in the blood of the conquered, caused them little 

 trouble ; they had acquired "tolerance" from long ages 

 of selection. Transmitted to the northerners, the 

 disease killed or debilitated, and gradually the darker 

 races, variously intermarrying with the lighter, came 

 to dominate the civilization. The chances for success in 

 life were in inverse proportion to the amount of north- 

 ern blood, when malaria became universal. In similar 

 ways we may explain how the northmen, the Normans, 

 firmly established themselves in northern France, but 

 have left no impression on the population of Sicily. All 

 these matters are of course largely speculative, viewed 

 after so great a lapse of time ; but we can at least show 

 that similar effects are being produced today, in Africa 

 and Alaska and in the islands of the Pacific. 



In the struggle for existence between races, the 

 existence of a mild disease in one is often the undoing 

 of the other. The disease is mild to those races which 



