In the case of accidental homicide, deference may also have to be shown for the supposed feelings of the dead man's ghost, which, angry and bloodless, is craving for revenge and thirsting for blood. To leave its desires ungratified would be both dangerous and unmerciful. That this has something to do with the rigid demand of life for life in the case of homicide by misadventure seems all the more likely as in some instances when the involuntary manslayer is pardoned, other blood is to be shed instead of his. Among the Yao and Wayisa, near Lake Nyassa, it is the custom "by way of propitiation to give up a slave or some relative of the criminal's, to 'go along with the one who was slain,' and this seems to be invariably done when one is killed by accident, in which case the slayer may escape, the deputy taking as it were his place."[111] We may assume that a similar idea underlies the ancient Roman law which provided a ram to be sacrificed in the place of the involuntary manslayer. [Footnote 111: Macdonald, in _Jour. Anthr. Inst._ xii. 108.] But the dead man's ghost not only persecutes his own family if **neglectful of their duty, it also attacks the manslayer {233} and cleaves to him like a miasma. The manslayer is consequently regarded as unclean, and has, both for his own sake and for the sake of the community in which he lives, to undergo some ceremony of purification in order to rid himself of the dangerous and infectious pollution. This notion will be illustrated in a following chapter. In the present connection I merely desire to point out that the pollution is there, whether the shedding of blood was intentional or accidental. And, as will be shown, though this state of uncleanness does not intrinsically involve guilt, it easily becomes a cause of moral disapproval, whilst the ceremony of purification is apt to be looked upon in the light of punishment. We shall also find that the notion of a persecuting ghost may be replaced by the notion of an avenging god, it being a fact of common occurrence that the doings or functions of one mysterious being are transferred to another. We shall, finally, see that the infection of uncleanness is shunned by gods even more than it is shunned by men; and this largely helps to explain the attitude of religion towards unintentional and unforeseen shedding of human blood.