Page:Popular Science Monthly Volume 48.djvu/866

784 The result of comparative study of the lower forms of life is suggestive in this connection. With plants and animals a sudden change of habitat will often produce a temporary sterility, which disappears only after a series of chance variations. The chrysanthemum remained infertile for sixty years after its introduction into France from China, so that continued importation of the seed was necessary. Finally, in 1852 a few plants developed seeds; and from these others were raised, until to-day the species is self-sustaining in Europe. A similar experience with corn at Sierra Leone, with the goose at Bogotá, and European poultry in America, is instanced by De Quatrefages. His rather optimistic argument with regard to the future of acclimatization is based, indeed, upon the study of animals and plants, rather than of man. He reasons by analogy that if fertility becomes re-established by spontaneous variation in this sphere, it may be likewise affirmed to be true for man, thus giving countenance to the view that climatic changes do indeed produce infertility.

Despite the authorities who hold on general principles that sterility in man follows—or at least that it ought to follow—a sudden change of climate, direct proof for it is very hard to find. Broca has indeed affirmed that the Mamelukes in Egypt became infertile for that reason; but in his case, as in all others, no attempt is made to eliminate a number of other factors. Jousset declares, on the contrary, that no direct effect upon fecundity can be traced to climate. Dr. Fritsche concedes that, although sterility may result, there is as yet no direct evidence to prove it. The difficulty, it will be observed, is to eliminate the effects of crossing with the natives, or else of marriage with newly arrived immigrants. A physician of twenty-seven years' experience in the Dutch Indies has never known a European family to keep its blood unmixed in this way for the necessary period of three generations. Only one example of pure isolation is known, in the island of Kisser, and sterility there is by no means certain.