The actual power of physical mediumship is a gift which is in some strange way connected with physiological conditions. It is often more marked in ill-health than when well and sometimes vanishes completely or may return again after a year or two. It has now been ascertained that the site of the haunting is the functioning factor and that one or other of the humans present is the often unconscious medium. If a known physical medium is substituted for the original one the phenomena will often be as effectively reproduced. The doctrine held by Spiritualists that a poltergeist is a low type of spirit essentially non-human and akin to the tree dryads or earth or air elementals does not seem to be borne out in practice. Just as many people hold that the bulk of harmless as distinct from malignant apparitions are “thought-impressions” on the surrounding walls which become visible to people with the gift of clairvoyance, so are there some grounds for believing that the poltergeist manifestations are due not to any directing intelligence at all but to the permanence of some old act or thought which still has in some cases the power of influencing matter. Mind cannot affect matter without the influence of a human intermediary. But the physical medium is a human intermediary and serves as a dynamo or battery for the generation of a necessary force. Just as table levitations and similar phenomena are produced by the extrusion of psychical rods or levers which are invisible,[46] but which are directed to a definite task by intelligence, so the poltergeist phenomena seem to be similar phenomena but without any directing intelligence. This statement needs qualification in the cases where the child medium has become partly aware that in some strange way he or she is the prime motor for the phenomena. Then the child’s mind consciously or subconsciously directing the impulse may focus the manifestation in the way of impish, malicious tricks afflicting an individual. The “psychic force” or psychoplasm extended by the medium is very closely akin to what is termed “animal magnetism”--it seems to be of nervous origin and physiologically connected with internal secretory organs. A slight nervous derangement of one of the many complexes associated with the age of puberty may quite conceivably endow occasional children with a transient power of physical mediumship. The next point is the accumulatory effect of surroundings. Here we are very much in the dark, but the manifestations do not occur unless physical limits, such as walls, are present. In a poltergeisted house two unconscious agents of the activities may, particularly while asleep, but also while awake, saturate the surroundings with this peculiar form of energy.