That the above-mentioned circles are so intimate and closed that strangers have great difficulty in gaining admittance to the seances is due to the fact that materialistically-minded sceptics have a tendency, out of mistaken zeal for "revealing deception", to interfere with the materialised forms or spirits, which can be extremely dangerous for the medium since the spirit's materialisation consists of the medium's A-substance and other psychic matter temporarily on loan to the spirit. If this matter is subject to violence during the materialisation, it not only destroys and prevents the spirit's concentration and A-power from being brought into play (so that the materialisation becomes impossible), but the medium too can be seriously hurt through such a brutal intervention. The fact is that when a connection and perfect contact have arisen between the spirit's A-power and the medium's A-substance the materialisation can gradually be of such an extent that it can to a certain degree cause the beginnings of a dematerialisation of the physical body of the medium himself. His cells begin to break up into A-substance, which thereby becomes accessible for the spirit's concentration and A-power and becomes matter in the new materialised form. During such a seance a part of the medium's physical and psychic body's particles are thus placed in the materialised form. It is obvious that the medium's life can thereby be in the most terrible danger if appropriate protection against the brutal interference of ignorant people during the seance is not arranged. If the bodily material lent by the medium becomes disarranged or mixed with foreign energies during the seance, it will, on rematerialisation in the medium's body, show a corresponding disorder. To the same extent that the cellular structure or material is not organized in its normal way, the medium's body will suffer damage in the places concerned. Materialisation-seances are therefore not things one can play with as a pleasant entertainment. It is a very serious process that ought to take place absolutely only in the presence of really expert and understanding people who are initiated into all the elements of danger.