398 THE POPULAR SCIENCE MONTHLY. 



character. In France the ponds of the Dombes and the mouth-country 

 of the Charente were, till recently, no less dangerous. Life in great 

 cities also seems to exercise a special influence on reproduction. Bou- 

 din could not find any pure Parisians who could trace the residence of 

 their ancestors in the city back for more than three generations. In 

 Besan9on the " old families " generally die out in not quite a hundred 

 years, and are replaced by families from the country ; and the same 

 is, to a greater or less extent, the case in London, Berlin, and other 

 large cities. 



Has it been proved that on ships, where men are crowded together 

 for months under conditions incompatible with health, particular dis- 

 orders are developed, to which sailors may, indeed, gradually accus- 

 tom themselves, but which are apt to mature into fatal maladies 

 among people hitherto in perfect health ? Can we, as Darwin sug- 

 gests, ascribe to such circumstances the fearful mortality and the 

 diminishing fruitfulness of the Polynesian races ? Does the consump- 

 tion which has become epidemic and hereditary in those islands be- 

 long to the diseases that have insinuated themselves there by the aid 

 of European sailors ? l^either the land nor the sky has changed since 

 the Polynesian archipelagoes were discovered; yet the aboriginal popu- 

 lation is diminishing at a really frightful rate, while its bastard off- 

 spring and the pure Europeans are increasing rapidly. 



To what extent the more or less pronounced dangerousness of a 

 locality is affected by normal conditions or by casual injurious influ- 

 ences is not always easy to estimate. The character of the soil, a 

 higher or lower temperature, dryness, and moisture, are not all that 

 determine the character of a country. We have evidence of this in 

 the fact that the process of acclimatization is not equally easy in both 

 hemispheres. The white races fare much better in the hot countries of 

 the southern hemisphere than in the corresponding latitudes of the 

 northern hemisphere. Between the thirtieth and thirty-fifth parallels 

 of latitude lie Algiers and a part of the United States — regions in 

 which the acclimatizing of Europeans is attended with great difiiculties. 

 In the southern hemisphere, the southern part of the Cape Colony and 

 !N'ew South Wales lie between the same parallels, and in those coun- 

 tries white men thrive. French and English troops exhibit a rate 

 of mortality eleven times as great in the northern as in the southern 

 hemisphere — a striking difference, which appears to depend upon the 

 greater frequency and intensity of miasmatic fevers. North of the 

 equator these fevers reach in Europe to the fifty-ninth degree of lati- 

 tude, while south of the equator they seldom extend beyond the 

 tropic and usually do not reach it. Tahiti lies under the eighteenth 

 degree of south latitude, and is free from fevers. French and English 

 troops stationed in the southern hemisphere afford a mean of 1*6 per 

 thousand sick with fever annually, while among those stationed in the 

 northern hemisphere the proportion of fever-sick is 224 per thousand. 



