The next step was to investigate the effect of bringing together the fingers of opposite hands.  I asked the subject to clasp his hands in such a way that the second phalanges would be about even.  I could not use the same apparatus conveniently with the hands in this position, but in order to have the contacts as similar as possible to those I had been using, I took four of the same kind of bullets and fastened them to the ends of two aesthesiometers.  This enabled me to give four contacts at once.  However, only two were necessary to show that contacts on fingers of opposite hands could be made to ‘fuse’ by putting the fingers together.  If two contacts are given on contiguous fingers, they are quite as likely to be perceived as one when the fingers are fingers of opposite hands, as when they are contiguous fingers of the same hand.

These results seem to show that one of the important elements of fusion is the actual space relations of the points stimulated.  The reports of the subjects also showed that generally and perhaps always they located the points in space and then remembered what finger occupied that place.  It was not uncommon for a subject to report a contact on each of two adjacent fingers and one in between where he had no finger.  A moment’s reflection would usually tell him it must be an illusion, but the sensation of this illusory finger was as definite as that of any of his real fingers.  In such cases the subject seemed to perceive the relation of the points to each other, but failed to connect them with the right fingers.  For instance, if contacts were made on the first, second and third fingers, the first might be located on the first finger, the third on the second finger, and then the second would be located in between.

So far my attention had been given almost entirely to fusion, but the tendency on the part of all subjects to report more contacts than were actually given was so noticeable that I concluded that diffusion was nearly as common as fusion and about as easy to produce.  It also seemed that the element of weight might play some part, but just what effect it had I was uncertain.  I felt, too, that knowledge of the apparatus gained through sight was giving the subjects too much help.  The subjects saw the apparatus every day and knew partly what to expect, even though the eyes were closed when the contacts were made.  A more efficient apparatus seemed necessary, and, therefore, before taking up the work again in 1900, I made a new apparatus.

Not wishing the subjects to know anything about the nature of the machine or what could be done with it, I enclosed it in a box with an opening in one end large enough to allow the subject’s hand to pass through, and a door in the other end through which I could operate.  On the inside were movable wooden levers, adjustable to hands of different width.  These were fastened by pivotal connection at the proximal end.  At the outer end of each of these was an