A curious application of the doctrine of contagious magic is the relation commonly believed to exist between a wounded man and the agent of the wound, so that whatever is subsequently done by or to the agent must correspondingly affect the patient either for good or evil. Thus Pliny tells us that if you have wounded a man and are sorry for it, you have only to spit on the hand that gave the wound, and the pain of the sufferer will be instantly alleviated.
