When a savage practises extraconjugal sexual intercourse, the act is frequently not, as it has come to be conventionally regarded in civilization, an immorality or at least an illegitimate indulgence; it is a useful and entirely justifiable act, producing definite benefits, conducing alike to cosmic order and social order, although these benefits are not always such as we in civilization believe to be caused by the act. Thus, speaking of the northern tribes of central Australia, Spencer and Gillen remark: "It is very usual amongst all of the tribes to allow considerable license during the performance of certain of their ceremonies when a large number of natives, some of them coming often from distant parts, are gathered together--in fact, on such occasions all of the ordinary marital rules seem to be more or less set aside for the time being. Each day, in some tribes, one or more women are told off whose duty it is to attend at the corrobboree grounds,--sometimes only during the day, sometimes at night,--and all of the men, except those who are fathers, elder and younger brothers, and sons, have access to them.... The idea is that the sexual intercourse assists in some way in the proper performance of the ceremony, causing everything to work smoothly and preventing the decorations from falling off."[184] It is largely this sacred character of sexual intercourse--the fact that it is among the things that are at once "divine" and "impure," these two conceptions not being differentiated in primitive thought--which leads to the frequency with which in savage life a taboo is put upon its exercise. Robertson Smith added an appendix to his _Religion of the Semites_ on "Taboo on the Intercourse of the Sexes."[185] Westermarck brought together evidence showing the frequency with which this and allied causes tended to the chastity of savages.[186] Frazer has very luminously expounded the whole primitive conception of sexual intercourse, and showed how it affected chastity.[187] Warriors must often be chaste; the men who go on any hunting or other expedition require to be chaste to be successful; the women left behind must be strictly chaste; sometimes even the whole of the people left behind, and for long periods, must be chaste in order to insure the success of the expedition. Hubert and Maus touched on the same point in their elaborate essay on sacrifice, pointing out how frequently sexual relationships are prohibited on the occasion of any ceremony whatever.[188] Crawley, in elaborating the primitive conception of taboo, has dealt fully with ritual and traditional influences making for chastity among savages. He brings forward, for instance, a number of cases, from various parts of the world, in which intercourse has to be delayed for days, weeks, even months, after marriage. He considers that the sexual continence prevalent among savages is largely due to a belief in the enervating effects of coitus; so dangerous are the sexes to each other