The instances of sympathetic magic are naturally divided into two main classes, which, broadly speaking, correspond to the two types of association. But just as in psychology it is often difficult to decide whether a given associative process has its origin in a relation of contiguity or in one of similarity, so it is often an open question to which group a given superstition is to be assigned. It may even be possible to deduce both groups from one common and fundamental magical principle. However the definitive theoretical explanation may turn out, we have for the present to uphold a distinction between the two forms. And in order to start from the facts that are simpler and easier to explain, we shall first devote our attention to _sympathetic magic based on a material connection between things_. The superstitious notions which can be brought together under this heading are familiar to every one. There is scarcely a single book on ethnology or folklore which does not present some illustrations of the belief that by acting upon a part of a given whole we may influence this whole as well as all its other parts. This universal doctrine of a solidarity between the things that have entered as parts in the same material totality has given rise all over the world to beliefs and practices which, although varying in details, are essentially similar in general character. We need only refer to the well-known folk-beliefs as to the necessity of caution in disposing of clippings of hair or nails, of saliva, or anything else removed from the human body. Such objects, it is supposed, would give any enemy into whose hands they might fall the power of injuring through them the person from whom they had proceeded.[467] Almost equally universal is the belief that close relatives, as being ingredients in—or perhaps rather partakers of—the same whole, the family, are bound together in a quite material solidarity of suffering. From the sociological point of view this group of superstitions, owing to the social importance of the last-mentioned totality, is of especial interest; and therefore the curious customs concerning the relation between a father and his unborn child, between husband and wife, ancestors and descendants, etc., which no doubt are all based on the idea of a material connection, have been treated of with due completeness in sociological literature.[468] Equally valuable for the psychological interpretation, although less pregnant with social import, are all the petty tricks of sorcery in connection with hunting, fishing, agriculture, and so on, which are practised even now among most European nations.[469] From the array of facts inserted by Mr. Hartland in his monumental commentary on the _Legend of Perseus_, we can form an opinion of the wide and deep-going influences which the belief in magical connection between things materially connected has exercised in all departments of life. And besides this ethnological apparatus, Mr.