61. In order to produce the phenomenon referred to, the presence of one or two
persons endowed with a special aptitude, and who are called Mediums, is necessary.
The number of co-operators is of no importance, except that, when there are a good
many, some of them may be found to be mediums. With regard to those of the
company who are not mediums, their presence is of no use, and may even be a
hindrance, through the qualities of mind or of temperament which they bring into the
The qualities of mediums are various. The medianimic power is sometimes
very strong, producing strongly marked effects; a single individual who is really a
powerful medium often producing more effect, alone, than twenty others united. If
such a one lays his hands on the table for an instant, it immediately begins to move,
rising up, turning over, spinning round with great velocity, or performing a variety of
irregular and often violent motions.