Probably in all such cases the rule is based on a fear of being brought into contact with blood, especially the blood of women. From a like fear a Maori will never lean his back against the wall of a native house.(650) For the blood of women is believed to have disastrous effects upon males. In the Encounter Bay tribe of South Australia boys are warned that if they see the blood of women they will early become gray-headed and their strength will fail prematurely.(651) Men of the Booandik tribe think that if they see the blood of their women they will not be able to fight against their enemies and will be killed; if the sun dazzles their eyes at a fight, the first woman they afterwards meet is sure to get a blow from their club.(652) In the island of Wetar it is thought that if a man or a lad comes upon a woman’s blood he will be unfortunate in war and other undertakings, and that any precautions he may take to avoid the misfortune will be vain.(653) The people of Ceram also believe that men who see women’s blood will be wounded in battle.(654) Similarly the Ovahereró (Damaras) of South Africa think that if they see a lying-in woman shortly after child-birth they will become weaklings and will be shot when they go to war.(655) It is an Esthonian belief that men who see women’s blood will suffer from an eruption on the skin.(656) Again, the reason for not passing under dangerous objects, like a vine or women’s blood, is a fear that they may come in contact with the head; for among primitive people the head is peculiarly sacred. The special sanctity attributed to it is sometimes explained by a belief that it is the seat of a spirit which is very sensitive to injury or disrespect. Thus the Karens suppose that a being called the _tso_ resides in the upper part of the head, and while it retains its seat no harm can befall the person from the efforts of the seven _Kelahs_, or personified passions. “But if the _tso_ becomes heedless or weak certain evil to the person is the result. Hence the head is carefully attended to, and all possible pains are taken to provide such dress and attire as will be pleasing to the _tso_.”(657) The Siamese think that a spirit called _Khuan_, or _Chom Kuan_, dwells in the human head, of which it is the guardian spirit. The spirit must be carefully protected from injury of every kind; hence the act of shaving or cutting the hair is accompanied with many ceremonies. The _Khuan_ is very sensitive on points of honour, and would feel mortally insulted if the head in which he resides were touched by the hand of a stranger. When Dr. Bastian, in conversation with a brother of the king of Siam, raised his hand to touch the prince’s skull in order to illustrate some medical remarks he was making, a sullen and threatening murmur bursting from the lips of the crouching courtiers warned him of the breach of etiquette he had committed, for in Siam there is no greater insult to a man of rank than to touch his head.