W. R. Smith, Kinship and Marriage in Early Arabia, 1885, p. 307. The point is elaborated in the same author's Religion of Semites, second edition, Appendix on "Holiness, Uncleanness, and Taboo," pp. 446-54. See also Wellhausen, Reste Arabischen Heidentums, second edition, pp. 167-77. Even to the early Arabians, Wellhausen remarks (p. 168), "clean" meant "profane and allowed," while "unclean" meant "sacred and forbidden." It was the same, as Jastrow remarks (Religion of Babylonia, p. 662), among the Babylonian Semites.
J. C. Frazer, The Golden Bough, Chapter IV.
E. Durkheim, "La Prohibition de l'Inceste et ses Origines," L'Année Sociologique, Première Année, 1898, esp. pp. 44, 46-47, 48, 50-57. Crawley (Mystic Rose, p. 212) opposes Durkheim's view as to the significance of blood in relation to the attitude towards women.