§ 4. But we may now proceed a step further. The excitation may be external not only in the sense of coming from the external organ, but in the sense of coming from the external world. It may be due not to any abnormality of the eye or the nerve, but to the ordinary stimulus of light-rays from real objects. Some interesting evidence on this point has been lately described by M. Binet.1 His experiments were conducted on five hysterical young women at the Salpetriere, who, when hypnotised, could be made to see anything that was suggested to them; and also on an insane patient at St. Anne, who had a standing visual hallucination of her own. The results confirmed the rule first enunciated by M. Fere - that "the imaginary object is perceived under the same conditions as a real one"; and to this M. Binet adds the further conclusion, that a sensation derived from a real external source, occupying the same position in space as the imaginary object seemed to occupy, was an indispensable factor of the hallucination. Space fails me to describe the results in detail.

It is enough to say that a prism applied to one eye doubled the imaginary object2; that a spy-glass removed or approximated it, according as the object-glass or eye-piece was applied to the patient's eye; that a mirror reflected the object and gave a symmetrical image of it; and that the optical effect, as regards angles of deviation and reflexion and all the details of the deception, was in every case precisely what it would have been had the object been real instead of imaginary. Here then we seem fairly driven outside the patient's own organism; the conclusion is almost irresistible that some point of external space at or near the seat of the imagined object plays a real part in the phenomenon. To this point M. Binet gives the name of point be repere; and he regards it as producing a nucleus of sensation to which the hallucination accretes itself. When the point de repere is in such a position as to be reflected by the mirror, then the imaginary object is reflected, and not otherwise; the object is, so to speak, attached to its point de repere, and will follow the course of any optical mutations to which its external nucleus is subjected.3

1In the Revue Philosophique, April and May, 1884.

2This observation was first made by M. Fere; see Le Progres Medical, 1881, p. 1041.

3The full explanation of these phenomena seems to be as follows. If the point de repere is not at, but close to, the spot where the imaginary object appears (as seems to have been the case in some of the experiments), there is no difficulty. The point de repere is then itself part of what is all along perceived; and in any effects produced on it by optical apparatus, it will carry the neighbouring object with it by association. If, however, the actual area covered by the object is sufficiently distinguished from its surroundings to act itself as point de repere, and no other possible points de repere exist in the field of vision, the case is different, but can still be explained. It will not be disputed that a slightly longer time is necessary for the formation of the image of a suggested object and the conversion of this image into a percept, than for the experience of sensation from an object actually before the eyes. When, therefore, the operator points to a particular place on the white table-cloth and says, ** There is a brown butterfly," we may suppose that in the patient's consciousness a real sensation of white precedes by an instant the imposed sensation of brown.

So when the cardboard on which a non-existent portrait has just been seen is again brought before the patient's eyes, it is almost certain that the recognition of it as the same piece of white cardboard (known by its points de repere) precedes by an instant the hallucinatory process and the reimposition of the portrait. That there is this instant of true sensation seems to be shown, indeed, by one of M. Binet's experiments. The optical effect to be expected. An experimenter who has not expressly recognised the reality of thought-transference would never think of so arranging his experiment that he himself should not know, till after the result, which instrument was in use or what was its position; nor indeed is it easy to imagine how such a condition could in practice be carried out. We have reason, moreover, to think that the hypnotic rapport, which enables the operator to impose a hallucination on the "subject," is a condition decidedly favourable to telepathic influence. The point seems worth suggesting, if only because thought-transference is a possibility which will assuredly need to be taken into account at many points, in that wide investigation of hysterical conditions which is assuming so much prominence in France. It would be most interesting if a state of hallucination turned out to be one in which the "subject" is specially susceptible to "transferred impressions".

In these cases, it will be seen, the experience was really a sort of monstrous illusion - totally different, however, from ordinary misinterpretations of sensory impressions; for we must beware of confounding the excitation that comes from the point de repere with the sensory element of the hallucination itself. The former is an unnoticed peg for the percept; the latter is its very fulness and substance, and is entirely imposed or evoked by the brain, not supplied to it. The type is too interesting to pass over: at the same time, I am bound to say that it seems to be extremely rare. I have made many endeavours to obtain the prism-effects with hypnotised (but not hysterical) "subjects"; but I have never succeeded, except when some conspicuous real object had first been put under the instrument, and the idea of doubling had thus been prominently suggested.1 Professor Bernheim, of Nancy, tells me that he has also made repeated trials, and has never confirmed the results of the Salpetriere. And one further reservation must be made.

It is just conceivable that the changes wrought on the imaginary percept were due, not to the optical instruments, but to thought-transference. For M. Binet and his assistants of course knew themselves, in each case, the particular patient having been made to see an imaginary portrait on a blank piece of cardboard, this was suddenly covered by a sheet of paper. The patient said that the portrait disappeared for a moment, but then reappeared on the paper with complete distinctness. We may thus fairly conclude that an area which was actually seen before the hallucination was induced in the first instance, will also be actually seen for a moment when vision is redirected to it (or its reflection), after the optical apparatus has been brought into play. During that moment, it will, of course, be seen under the newly introduced optical conditions; and association may again cause the object which supplants it to follow suit. It is quite possible, however, to suppose that the supplanted area continues further to provoke the hallucination, in the same sense that the white rays provoked the green percept in Fechner's experiment.

The rays which are lost to consciousness continue to excite the sensorium physically; and this physical excitation will have definite peculiarities, corresponding to the distinguishing marks of the area whence it comes. Double this excitation by a prism, or reflect it from another quarter, and the percept which it provokes may naturally be doubled or seen in the new direction. So, if both eyes were employed in Fechner's experiment (pp. 290-1), might the green percept be artificially doubled.

1In this connection, I may quote the following spontaneous case - where the imagination of the percipient may probably have been adequate to conjure up the reflected figure. The account is from Mr. Adrian Stokes, m.r.c.s., of 16, Howell Road, St. David's, Exeter.

'* When I was living in Bedford Street North, Liverpool, in the year 1857 (I think), my wife roused me from sleep suddenly and said, ' Oh! Adrian, there's Agnes! ' I started up, crying, 'Where? Where?' but, of course, there was no Agnes. My wife then told me that she had awoke, and had seen the form of her only sister, Agnes, sitting on the ottoman at the foot of the bed. On seeing this form she felt frightened; but then, recalling her courage, she thought if the figure were real she would bo able to see it reflected in the mirror of the wardrobe, which she had in full view as she lay in bod. Directing her eyes, therefore, to the mirror, there she saw, by the light of the fire that was burning brightly in the grate, the full reflection of the form seated on the ottoman, looking at a bunch of keys which she appeared to hold in her hand. Under the startling effect caused by this sight, she called me to look at it, but, before I was awake, the form and its reflection had vanished. It was not a dream, my wife is certain.

"When my wife saw her sister sitting at the foot of our bed looking at the bunch of keys, she (the sister) was clad in the ordinary indoor dress of the time. I remember the start of surprise with which I awoke and exclaimed. My wife has never, that I know of, experienced any hallucination or delirium; and is a woman of excellent sense and judgment. She never saw any other vision but that one".