regard to longevity there is a wide variation in fam ilies in the same community, in social classes, in the sexes, and iu local ities, but probably not in races. The normal average age of man was calculated by the eminent physiologist Flourens to be about one hundred years. He based his estimate on the relation which the average length of life in the higher mammals bears to the period of utero-gestation, to the time required to complete their growth, and to their attainment of puberty. While thus his conclusion has strong foundation in analogy of other species, it is far from holding true for man—either, as Flourens maintained, because he does not live the life best suited to him, or for some unknown reason. Searching inquiry where careful records have been kept has constantly reduced the number of alleged centenarians. The average duration of human life is about the third of a century, and this appears to hold good in all races except where interfered with by preventable causes, as habits, unwholesome food, epidemics, and the like. Probably as striking an example of authentic longevity in a community as can be adduced is that recorded by a visitor to one of the missions of Lower California. In a village of about two hundred and fifty souls he found six persons over one hundred years, all in fair possession of their faculties, and their ages guaranteed by the records of the mission. They all belonged to the pure native stock.
Tolerance of the tolerance of disease there would seem at first sight to be a wide diversity in the races of man. For instance, a disease so little feared in most civilized countries as measles becomes a frightful pestilence among some savage tribes. By it alone in some of the Polynesian islands almost the whole native population has been swept away. Among the Central American tribes it has been more fatal than the smallpox. But medical science explains away this seeming intoler ance of disease in these lower races. The mildness of these epidemics in civilized communities arises from the fact that through an exposure extending over many generations all those peculiarly prone to their poison have been extinguished, and those who survived were such as transmitted to their descendants a certain insusceptibility to the poison of the epidemic. That this is the correct solution, and that this toler
ance is not a matter of race, was proved sadly enough in the case of the measles by the example of the Faroe islanders. This remote group to the north of Scotland, peopled exclusively by whites, had never, so far as known, had this disease brought to its shores until in the last century, when it was imported on a fishing vessel. It immediately became epi demic on the islands, attacking adults and children indiscriminately, and caused a mortality comparable to that which resulted from its introduc tion among the Maoris of New Zealand.
Fertility of with reference to the fertility of marriages it has not been shown that any material differences exist between different races. The prevailing notion that the lower races, as the American Indians, are less productive than the higher, has arisen from not taking into account the prevalence of abortion and infanticide, the marriage of girls of too tender an age, the early exhaustion of women by severe labor, and like incidental causes, which certainly limit the families, but do not tell against the fertil ity of the race when under favorable circumstances. The American Indians on the reservations have families quite as large as their white neighbors. Even the products of crosses between races are entirely fertile, although the contrary has been repeatedly stated.
Other are other variations sometimes referred to race, but which belong properly to nations, or even to limited branches of a nation. Such is the obliquity of the eye among the Japanese and Chinese. It is esteemed by them a mark of beauty (pl. I, figs. I, 2, 3, 4). It is, however, neither coextensive with the Mongolian race nor confined to it. The traveller D'Orbigny met a tribe in South America with just such Mongoloid eyes. The shape of the orbit does not cause this pecu liarity, as it depends entirely on the disposition of the soft parts of the face.
Not less singular is the extraordinary development of the nates in the Hottentot women, sometimes to such an extent that they cannot rise when in a sitting posture (Sir Andrew Smith), but, like the foot of a Chinese woman (fil. 1, fig. 5), there is reason to believe this is the product of sedulous cultivation, aided by transmission.