After the legal aspect of marriage has thus been established, it may be pointed out that several of the features of Australian marriage and betrothal set up, besides these legal bonds, other ties which in themselves lead to the carrying out of marriage, and afterwards keep husband and wife together. In the first place, exchange of women. When a man was to receive a wife in exchange for his relative, it is clear that he felt himself strongly bound to keep his promise; for he lost as much as his partner in case he broke the agreement. We saw also that betrothal established a certain status between the families of the male and the female respectively. This status, the main feature of which was exchange of gifts, with a preponderance of the male's gifts and duties, such as providing food, created certain obligations which further enforced the validity of the contract. As pointed out above, we can even find, at least in the Central and Northern tribes, clear features of marriage by purchase. Equally important in this light is the fact of exchange of females. This has its theoretical consequences. The two main facts of collective psychology, expressed by marriage by purchase, are (1) that there is a certain value attached to the woman and expressed by the conventional price; (2) that there is the idea of right of property or at least of the individual personal right of the husband over his wife, acquired by him through the fact of purchase. These two facts are very important. For both these sets of ideas can only have been evolved in a society where individual marriage was a well-known, well-recognized and fundamental institution. There would have been no reason to pay for a wife if the possession of her would confer no positive rights on the owner. The following point may also be adduced here, viz. that generally the old men and other men of influence and power secured the young females of the tribes. It was easier for influential and important men to maintain their right over their wives before as well as after actual possession. Besides, we are informed by all (with the exception of R. H. Mathews) that the rules of exogamy were very strong, excluding in the majority of tribes a good number of females from all attempts by the males of forbidden classes. This undoubtedly contributed also to increase the security and validity of the marital union, by reducing to very few the number of the men who were in a position to interfere with the rights of the husband.