EUGENICS 19
as compared to the natives of the densely populated parts of Europe and Asia, have undergone little evolution against consumption. As a consequence, no African colony has ever succeeded in Europe or Asia. For instance, the Dutch and English imported about twelve thousand negroes into Ceylon a century ago. Within twenty years all had perished, mainly of consumption, and that in a country where the disease is not nearly so prevalent as in northern Europe, or the more settled parts of northern Asia.
There can be little doubt that the sterility of the New World races when brought into contact with civilization is due mainly to ill-health. The sterility of our upper classes is mainly voluntary. It is due to the possession of special knowledge. The growing sterility of the lower classes is due to the spread of that knowledge ; hence the general and continuous fall in the birth-rate. Until we are able to estimate the part played by this knowledge it would be vain to collect statistics of comparative sterility.
We have frequently been told that no city family can persist for four generations unless fortified by country blood. That, I believe, is a complete error. Country blood does not strengthen city blood. It weakens it, for country blood has been less thoroughly purged of weak elements. It is true, owing to the large mortality in cities and the great immigration from the country, it is difficult to find a city family which has had no infusion of country blood for four generations. But to suppose on that account that country blood strengthens city blood against the special conditions of city life is to confuse post hoc with propter hoc.
Slum life and the other evil influences of civilization, including bad and insufficient food, vitiated air, and zymotic diseases, injure the individual. They make him acquire a bad set of traits. But they do not injure the hereditary tendencies of the race. Had they done so, civilization would have been impos- sible. Civilized man would have become extinct. On the contrary, by weeding out the unfittest, they make the race strong against those influences.
If, then, we wish to raise the standard of our race, we must do it in two ways. In the first place, we must improve the conditions under which the individual develops, and so make him a finer animal. In the second place, we must endeavor to restrict, as much as possible, the marriage of the physically and mentally unfit. In other words, we must attend both to the acquired characters and to inborn characters. By merely improving the conditions under which people live we shall improve the individual, but not the race. The same measures will not achieve both objects. Medical men have done a good deal for the improvement of the acquired characters of the individual by improving sanitation. They have attempted nothing toward the second object, the improve- ment of the inborn traits of the race. Nor will they atempt anything until they have acquired a precise knowledge of heredity from biologists. On the other hand, before biologists are able to influence medical men they must bring to bear their exact methods of thought on the great changes produced in various races by their experience, during thousands of years, of disease. I am sure our knowledge of heredity will gain in precision and breadth by a consideration of these tremendous, long-continued, and drastic experiments conducted by nature. No experiments conducted by man can compare with them in magnitude and completeness. And, as I have already intimated, the precise statistical informa- tion on which our conclusions may be based is already collected and tabulated. I am quite sure it is good neither for medicine nor biology that medical men and biologists should live as it were in separate and closed compartments, each body ignoring the splendid mass of data collected by the other. Much of medicine should be a part of biology, and much of biology a part of medicine.
BY W. LESLIE MACKENZIE, M.A., M.O.
It is to me a great privilege to be permitted to say something in any discussion where Dr. Francis Galton is leader ; because from early in my student days until now I have felt that his method of handling sociological facts has always been at once scientific and practical. Whether the ideas he represents have had some subconscious effect in driving me into the public-health service,
