The form of marriage, as stated above, was the pairing family in gradual transition to monogamy. It was not yet strict monogamy, for polygamy was permitted for the wealthy. Chasteness of the girls was in general carefully maintained, different from the custom of the Celts. Tacitus speaks with special ardor of the sacredness of the matrimonial bond among the Germans. Adultery of the woman is alone quoted by him as a reason for a divorce. But his treatment of this subject leaves many a flaw and besides, it too openly holds up the mirror of virtue to the dissipated Romans. So much is certain: Granted that the Germans were such exceptional models of virtue in their forests, it required only a short contact with the outer world to bring them down to the level of the other average Europeans. In the whirl of Roman life the last trace of pure morals disappeared even faster than the German language. Just read Gregorius of Tours. It is obvious that in the primeval forests of Germany no such hyper-refined voluptuousness could exist as in Rome. That implies fully enough superiority of the Germans over the Roman world, and there is no necessity for ascribing to them a moderation and chastity that have never been the qualities of any nation as a whole. A result of gentile law is the obligation to inherit the enmities as well as the friendships of one's father and relatives; so is furthermore the displacement of blood revenge by the Wergeld, a fine to be paid in atonement of manslaughter and injuries. A generation ago this Wergeld was considered a specifically German institution, but it has since been found that hundreds of nations introduced this mitigation of gentile blood revenge. Like the obligatory hospitality, it is found, for instance, among the American Indians. Tacitus' description of the manner in which hospitality was observed (Germania, chapt. 21) is almost identical with Morgan's.