At an early stage of culture, again, menstruation is regarded as a process of purification, a dangerous expulsion of vitiated humors. Hence the term _katharsis_ applied to it by the Greeks. Hence also the mediæval view of women: "_Mulier speciosa templum ædificatum super cloacam_," said Boethius. The sacro-pubic region in women, because it includes the source of menstruation, thus becomes a specially heightened seat of taboo. According to the Mosiac law (Leviticus, Chapter XX, v. 18), if a man uncovered a menstruating woman, both were to be cut off. It is probable that the Mohammedan custom of veiling the face and head really has its source solely in another aspect of this ritual factor of modesty. It must be remembered that this custom is not Mohammedan in its origin, since it existed long previously among the Arabians, and is described by Tertullian.[43] In early Arabia very handsome men also veiled their faces, in order to preserve themselves from the evil eye, and it has been conjectured with much probability that the origin of the custom of women veiling their faces may be traced to this magico-religious precaution.[44] Among the Jews of the same period, according to Büchler,[45] the women had their heads covered and never cut their hair; to appear in the streets without such covering would be like a prostitute and was adequate ground for divorce; adulterous women were punished by uncovering their heads and cutting their hair. It is possible, though not certain, that St. Paul's obscure injunction to women to cover their heads "because of the angels," may really be based on the ancient reason, that when uncovered they would be exposed to the wanton assaults of spirits (1 Corinthians, Ch. XI, vv. 5-6),[46] exactly as Singhalese women believe that they must keep the vulva covered lest demons should have intercourse with them. Even at the present day St. Paul's injunction is still observed by Christendom, which is, however, far from accepting, or even perhaps understanding, the folk-lore ground on which are based such injunctions. Crawley thus summarizes some of the evidence concerning the significance of the veil:--