The importance of recognizing the special sense in which the word "unclean" is used in this connection was clearly pointed out by Robertson Smith in the case of the Semites. "The Hebrew word _tame_ (unclean)," he remarked, "is not the ordinary word for things physically foul; it is a ritual term, and corresponds exactly to the idea of _taboo_. The ideas 'unclean' and 'holy' seem to us to stand in polar opposition to one another, but it was not so with the Semites. Among the later Jews the Holy Books 'defiled the hands' of the reader as contact with an impure thing did; among Lucian's Syrians the dove was so holy that he who touched it was unclean for a day; and the _taboo_ attaching to the swine was explained by some, and beyond question correctly explained, in the same way. Among the heathen Semites,[362] therefore, unclean animals, which it was pollution to eat, were simply holy animals." Robertson Smith here made no reference to menstruation, but he exactly described the primitive attitude toward menstruation. Wellhausen, however, dealing with the early Arabians, expressly mentions that in pre-Islamic days, "clean" and "unclean" were used solely with reference to women in and out of the menstrual state. At a later date Frazer developed this aspect of the conception of taboo, and showed how it occurs among savage races generally. He pointed out that the conceptions of holiness and pollution not having yet been differentiated, women at childbirth and during menstruation are on the same level as divine kings, chiefs, and priests, and must observe the same rules of ceremonial purity. To seclude such persons from the rest of the world, so that the dreaded spiritual danger shall not spread, is the object of the taboo, which Frazer compares to "an electrical insulator to preserve the spiritual force with which these persons are charged from suffering or inflicting, harm by contact with the outer world." After describing the phenomena (especially the prohibition to touch the ground or see the sun) found among various races, Frazer concludes: "The object of secluding women at menstruation is to neutralize the dangerous influences which are supposed to emanate from them at such times. The general effect of these rules is to keep the girl suspended, so to say, between heaven and earth. Whether enveloped in her hammock and slung up to the roof, as in South America, or elevated above the ground in a dark and narrow cage, as in New Zealand, she may be considered to be out of the way of doing mischief, since, being shut off both from the earth and from the sun, she can poison neither of these great sources of life by her deadly contagion. The precautions thus taken to isolate or insulate the girl are dictated by regard for her own safety as well as for the safety of others.... In short, the girl is viewed as charged with a powerful force which, if not kept within bounds, may prove the destruction