290 THE PRESENT EVOLUTION OF MAN — PHYSICAL 



Thousands of our race, who are unable to resist the 

 attacks of tuberculosis in their native land, and on that 

 account are obliged to leave it, are able to maintain a 

 healthy existence under conditions that yet prevail in 

 all such parts of the New World as have not long been 

 settled by us — in certain parts of America, in Australia, 

 in New Zealand, in the Pacific Islands, and also in 

 South Africa ; but in these very lands, where the less 

 resistant among us even recover from previous infection, 

 tuberculosis is causing the extinction of the natives. 

 This one fact throws the greatness of our evolution into 

 startling relief, for the natives usually live under hygienic 

 conditions that are far better as regards the disease than 

 do the settlers. The latter endeavour to reproduce their 

 home life as nearly as possible ; they gather themselves 

 into urban communities, and build much the same kind 

 of houses as those in which they contracted the disease ; 

 whereas the natives dwell scattered, or at most in small 

 communities, and in dwellings more wind-swept than 

 the shanties of tbe Hebridean fisher-folk, among whom 

 consumption is practically unknown. Nevertheless they 

 perish, and their races are becoming extinct, for, so sus- 

 ceptible are they, that they take the disease in circum- 

 stances under which the most susceptible Europeans live 

 immune ; and they are so little resistant that they take 

 it in its most virulent form. The microbes, unchecked 

 by the phagocytes, multiply within them at a rapid rate ; 

 they exhibit all the phenomena of galloping consump- 

 tion ; and even in their draughty wigwams and whares 

 they infect their fellows. To infect a normal European 

 a considerable dose of the virus seems necessary, since 

 many of the bacilli succumb in the conflict with the 

 phagocytes; to infect a Red Indian, or a Maori, the 

 smallest possible dose seems sufficient, since the 

 phagocytes appear to have no power of destroying the 

 bacilli. 



