Page:George Archdall Reid 1896 The present evolution of man.djvu/302

290 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 the Hebridean fisher-folk, among whom consumption is practically unknown. Nevertheless they perish, and their races are becoming extinct, for, so susceptible are they, that they take the disease in circumstances 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 consumption; 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.