538 D. The mystery of the organic effects of hypnotism lies bound up with the mystery of the Restitution of Function. Functions of the brain - motor, sensory, intellectual - which have been destroyed for a time by operations on animals or by disease in man, tend often to re-establish themselves, in part, at least, through the vicarious action of other nervous centres which learn to perform tasks unknown to them before. (See James, Principles of Psychology, vol. i. p. 67.) Here we have the vis re-paratrix Natura carried to the highest point to which it will go in man.

In my view, such substitutions of faculty are subliminally guided, and since hypnotic suggestion is an appeal to and a furtherance of subliminal faculty, it seems to me natural that it should bring about, not only such restitutions of function after mutilation, but also other educations and developments of nervous centres, whose result may often involve recovery from some apparently hopeless organic malady.

539 A. In the Revue Philosophique for November 1886 M. Bergson, of Clermont-Ferrand, gives an account of a case of supposed thought-transference or clairvoyance which turned out to be much more probably explicable by hypnotic hyperacuity of vision. The following is a summary and discussion of the case which I contributed to Mind for January 1887.

MM. Bergson and Robinet found that a boy, who was supposed to be a clairvoyant, or a telepathic percipient, could read figures and words under the following conditions. One of the observers hypnotised the boy, stood with his back nearly against the light, opened a book at random, held it nearly vertically facing himself, at about four inches from his own eyes, but below him, and looked sometimes at the page and sometimes into the boy's eyes. The book had often to be slightly shifted, but ultimately the boy could generally read the number of the page. Asked where he saw it, he pointed to the back of the book, just opposite the number's true position. Asked where the binding of the book was, he put his hand underneath the book, and indicated the place where the binding would have been had the book faced him.

It occurred to M. Bergson - and he deserves full credit for being the first to insist on this precaution - that, small though the figures were, the boy might really be reading them as reflected on the cornea of the hypnotiser. Experiments with slightly altered position showed that, in fact, the boy could not read the letters unless adjustment and illumination were carefully made as favourable as possible. The letters were 3 mm. in height - nothing is said of their thickness - and their corneal image would be about o. 1 mm. in height, as M. Bergson computes, under the conditions employed. This seems a very small image to see distinctly; but Mr. J. N. Langley and Mr. H. E. Wingfield, who have kindly tried some careful experiments to test this point, inform me that they can read on each other's corneæ the corneal image of printed letters of about 10 mm. in height. We know from Binet and Féré's experiments, etc, how greatly the hypnotic state does sometimes increase acuity of vision; and we may, I think, conclude that the boy probably did read the letters on his hypnotiser's cornea.

What, then, are we to make of the boy's statement that he saw the words as though in a book facing him ? M. Bergson feels sure that this was the boy's real belief. There was no suspicion of charlatanism, and, in fact, the boy disliked the experiments, and now, as M. Bergson writes to me, refuses to renew them. II. Bergson supposes, and I think justly, that this was a case of simulation inconsciente; the hypnotised subject genuinely referring his sensations to the source to which his First hypnotiser (a believer in thought-transference) had suggested to him that they were due.

And, in fact, this unconscious simulation which leads the subject to refer his unusual sensations to the special cause which his hypnotiser, or some caprice of his own mind, suggests, is a not uncommon and a very interesting phenomenon. It was observed, for instance, by Elliotson, who pointed out a good many hypnotic peculiarities which his successors are now gradually rediscovering. It is a hypnotic exaggeration of a familiar phenomenon, namely, of the large infusion of erroneous inference which we most of us import into the account which we render to ourselves of our ordinary sensations.

A particularly curious case is briefly described in the Journal of the Society for Psychical Research, June 1884. A man was brought to us who, when hypnotised, could often name cards held in front of him, although his eyes had been plastered up and bandaged in a most elaborate way. The man's friends took this for clairvoyance, and the man assented, being sure that he could not see the cards in the usual way. They "flashed upon him," as he said. Now, after a good deal of puzzling over the case, Mr. R. Hodgson found that he also could sometimes manage to see over similar bandages, through small chinks between the skin and the paper gummed over the eyes. But he, too, found that he saw fitfully, the power of vision seeming to come and go, - and he actually could not tell with which eye he was seeing, except by covering each eye in turn with his hand. The distorted position of the eyeball, and the minute and oddly-placed channels of vision, produced so much confusion that there seemed no reason to suppose that the hypnotised subject's belief that he was seeing "clairvoyantly " was other than genuine.

The case of M. Bergson's boy seems to have been a similar one. And his idea that he was reading from the book seems to have been a sort of compromise between the feeling that he was reading somewhere and the hypno-tiser's suggestion that the words were being transferred supernormally from mind to mind.

Thus far, then, M. Bergson's narration and explanation seem credible enough, and his argument as against thought-transference in this boy's case seems well made out. But he proceeded to further experiments which, as recounted, seem incredible, and which may lead some readers to distrust the accuracy of the whole series.

To explain the difficulty I must first point out that the word hyperæsthesia is loosely used for three different classes of phenomena. It is used (1) for an exaggeration of the familiar action of specialised organs, as when the eye is sensible to very small amounts of light. It is used (2) for alleged perceptions, which would imply a specialisation of what I may term our undifferentiated fund of nervous sensibility in novel directions. Sensibility to the action of magnets, of metals in contact, of medicaments at a distance, may or may not exist, but should scarcely be called by the same name as (say) the eye's extra sensitiveness to light. And again, the word is used (3) for cases where our non-specialised organs are credited with performing functions which, so far as we can see, demand a definite sense-specialisation, or our specialised organs are credited with functions which, on measurable anatomical grounds, appear to overpass the limits of their specialisation. This last class of cases must be received with extreme caution.

Well, M. Bergson says that he showed the boy a microscopic photograph of twelve men, its longest diameter 2 mm., and that the boy saw and imitated the attitude of each man. Also that he showed the boy a microscopic preparation, involving cells not greater than.06 mm. in diameter, and that the boy saw and drew these cells.

Now I might, in the first place, object that thought-transference was not formally excluded, since M. Bergson himself knew the photograph and the look of the cells. I do not press this, for the other experiments seem to me to negative thought-transference in this case. I merely point out that if we wish to prove that a subject does not receive an image from our minds, we should present to him an object with which we are ourselves unacquainted.

But the real difficulty is as regards the minimum visibile. It is usually (though not universally) supposed that in order to produce a definite image more than one retinal rod or cone must be stimulated; and that consequently no object can be separately discernible which does not subtend (say) an angle of 60 seconds, or whose retinal image is less than (say).004 mm. in diameter. Floating particles, none of them exceeding.0029 mm. in diameter, have, I believe, been seen as a cloud in a ray of electric light sent through a tube of filtered air, but have never been seen separately by the naked eye.

Now, the retinal image of an object itself only.06 mm. in diameter, and placed within the range of distinct vision, will be much less than.004 mm. in diameter. To bring it up to this minimum the retinal image must be 1/15 of the size of the object itself; and this implies a nearness to the eye involving mere darkness and blur. The microscopic slide was presumably transparent", but nothing was said as to the transparency of the photograph, and yet the points distinctly visible on the photograph must have been even smaller than the cells on the slide.

A letter with which M. Bergson has favoured me has done much to remove these difficulties. It seems that the photograph was transparent, and that the boy held it close to his eye. Moreover, after seeing the photograph the boy could not read ordinary print. "C'est trop grand," he said; and it was some time before the eye (which M. Bergson believes to have been always myopic) resumed its normal state. It seems, then, conceivable that hypnotic suggestion had induced (by spasm of the ciliary muscle?) some change in the shape of the crystalline lens, which made the eye a microscope for the time being. Mr. George Wherry has kindly communicated to me two somewhat analogous cases, where ciliary spasm (itself induced by microscopic or telescopic work) led to uniocular diplopia, in one case even triplopia. In these cases irregular ciliary spasm apparently turned the lens into a kind of multiplying glass: is it possible that M. Bergson induced a regular ciliary spasm, which turned the lens into a magnifier?