This, however, is but one of the ways in which supernatural beliefs become associated with sexual phenomena. In truth, there is not a stage of any importance in the sexual life of men and women where the same association does not transpire. There is, for example, the important phenomenon of puberty--important from both a physiological and sociological point of view. Pubic ceremonies of some kind are found all over the world, and in all forms, from those current amongst savages up to the contemporary practice of confirmation in the Christian Church. At all stages the period of puberty is the time of initiation. With uncivilised peoples a very general rule is the separation of the sexes, with fasting. Mr. Stanley Hall in his elaborate work on _Adolescence_ has dealt very exhaustively with these customs, with which we shall be more closely concerned when we come to deal with the subject of conversion. At present it is only necessary to point out that the governing idea is that at puberty the boy and the girl are brought into special relationship with the tribal spirits, the proof of which relationship lies in the sexual functions originated. With boys, once puberty is attained, the sexual development is orderly and unobtrusive. In the case of girls certain recurring phenomena make the essential fact of sex much more impressive to the primitive mind, with far-reaching sociological consequences. "Ignorance of the nature of female periodicity," says A. E. Crawley, "leads man to consider it as the flow of blood from a wound, naturally, or more usually, supernaturally produced."[69] In Siam an evil spirit is believed to be the cause of the wound. Amongst the Chiriguanas the girl fasts, while women beat the floor with sticks in order to drive away "the snake that has wounded the girl." Similar beliefs are found very generally among people in a low stage of culture, and customs and beliefs still surviving among people more advanced point to the conclusion that convictions of the same kind were once fairly universal. It is this function, combined with the function of childbirth, that brings woman into close contact with the supernatural world, makes her an object of fear and wonder to primitive man, accounts for a number of the customs and beliefs associated with her, and finally helps to determine her social position. It is because her periodicity is taken as evidence of her communion with spiritual forces that special precautions have to be taken concerning her. She becomes spiritually contagious. Thus, the natives of New Britain, while engaged in making fish-traps, carefully avoid all women. They believe that if a woman were even to touch a fish-trap, it would catch nothing. Amongst the Maoris, if a man touched a menstruous woman, he would be taboo 'an inch thick.' An Australian black fellow, who discovered that his wife had lain on his blanket at her menstrual period, killed her, and died of terror himself within a fortnight.