The other factor, which is really promoting the gradual disappearance of the Anglo-Saxons from the United States, is of a very different character. The descendants of the old immigrants are on the whole the aristocracy of the country. Now it is a law which hardly admits of exceptions, that aristocracies do not maintain their numbers. The ruling race rules itself out; nothing fails like success. Gibbon has called attention to the extreme respect paid to long descent in the Roman Empire, and to the strange fact that, in the fourth century, no ingenuity of pedigree makers could deny that all the great families of the Republic were extinct, so that the second-rate plebeian family of the Anicii, whose name did appear in the Fasti, enjoyed a prestige far greater than that of the Howards and Stanleys in this country. Our own peerage consists chiefly of parvenus. Only six of our noble families, it is said, can trace their descent in the male line without a break to the fifteenth century. The peerage of Sweden tells the same tale. According to Gallon, the custom or law of primogeniture, combined with the habit of marrying heiresses who, as the last representatives of dwindling families, tend to be barren, is mainly responsible for this. Additional causes may be the greater danger which the officer-class incurs in war, and, in former times, the executioner's axe. In our own day the reluctance of rich and self-indulgent women to bear children is undoubtedly a factor in the infertility of the leisured class.