603 A. Since Mr. Galton's well-known work we have become familiar with " number-forms " and other visual schemata of thought, which tend to shape themselves in many minds. These number-forms involve a complex internal visualisation, the mind's eye following their apparently fixed lines and angles; but they are also sometimes externalised by the subject. Professor Flournoy thus describes the case of M. Yowanovitch, an intelligent student at Geneva.1

M. Y. is an excellent visual, of the geometrical rather than the picturesque type. He has no trace of coloured audition; but on the other hand possesses well-defined and localised visual schemata for the numerals, the days of the week, the months, etc His number-form, composed of parallel lines representing the hundreds, occupies the right half of the space in front of him. In the left half floats his diagram of the week in the form of a horizontal rectangular figure divided into seven bands, something like a leaf of ruled paper, floating in the air about a metre from him, opposite his left thigh. Still more to the left, and at the height of his head, is situated his year-form, an ellipse of small eccentricity presented in a nearly vertical plane. Whenever M. Y. thinks of a date of the year, of a day past or future of the current week, or of a number, he perceives it in its proper place on the corresponding schema. I have often had occasion to make him write down rapidly a series of figures at random; now these figures do not flow of themselves from his pen; nor are they preceded in him by their auditory, motor, or graphic image; but he is obliged, in order to write them, to choose them on his number-form as on a picture placed in front of him.

For this purpose, he does not look straight at the page over which his pen is travelling, but looks to the side and above the paper in the direction of the internal diagram, which is the central object of his attention. He follows what he is writing only with an indirect vision, like a hurried copyist who lets his hand work of itself and will not lose sight of the page which he has to copy.

It will be observed that this case presents a curious analogy with the "arithmetical prodigies" on whom I dwelt in Chapter III (Genius). With some of them there was a kind of mental blackboard on which the figures which were to be added up remained visible as long as needed. But in their case the subliminal self supplied also the calculating facility; in M. Y.'s case it seems only to have stereotyped the visual framework for common mental operations.

1 Archives des Sciences Physiques et Naturelles, vol. xxviii., No. 10, October 15th, i892, pp. 326-27. Geneva.

We take one step further in the direction both of the definite character and of the potential externalisation of these subliminal quasi-percepts when we pass - by gradual transitions - from number-forms to audition coloree. A number-form is an association of an image with an idea - presumably as entirely a result of post-natal experience as is my association of my friend's face with his name. And so also indeed audition coloree, the perception of a definite "imaginary" or "subjective" colour in association with each definite actual sound, - may in some slighter cases be due to post-natal (mainly infantile) experience working upon an innate predisposition. But when the synesthesiæ of which sound-seeing is only the most conspicuous example are found in fuller development; - when gradated, peremptory, inexplicable associations connect sensations of light and colour with sensations of temperature, smell, taste, muscular resistance, etc, etc.; - for M. Gruber finds that these links exist in yet unexplored variety; - then it becomes probable that we are dealing, not with the casual associations of childish experience, but with some reflection or irradiation of specialised sensations which must depend on the connate structure of the brain itself.1 And the degree of precision shown in these entencephalic reflexes, - if I may so term them, - seems to exceed the precision attainable by the voluntary attention of the supraliminal self.

603 B. A striking case, combining both the subliminal intelligence and the visual externalisation, was described by Professor Gruber, of the University of J assy, Roumania, at the International Congress of Experimental Psychology in London, August 1892. In one self-observer of exceptional endowment, M. Gruber finds that the "chromatisms," as he calls them, - the patches of colour accompanying the audition of particular words, - follow certain definite rules as to size and shape, depending partly on the phonetic, and partly on the intellectual, significance of the word which the subject heard.2 This curious fact would obviously have remained unprovable had there been no possibility of objective measurement. But this possibility fortunately exists.

1 This view is consistent with the results of an Enquête sur l'audition colorée conducted by Professor Flournoy, from which it appears that of 213 persons presenting these associations only 48 could assign the date of their origin; and is supported by a case described in the Revue de l'Hypnotisme, December 1892, p. 185, where a man who had long exhibited a limited form of audition colorée developed gustation colorée in addition when in a low state of health.

2 For a full description of this case, see the "Report of the International Congress of Experimental Psychology, Second Session, London, 1892," pp. 10-20 (Williams & Norgate, London, 1892).

"My subject," says M. Gruber, "has the power of externalising his chroma-tisms; he projects them, for instance, upon the opposite wall, at no matter what distance. I chose a distance of three metres, which is that at which his vision is most distinct. I then made a circle of white paper which I supposed to be of the same size as his chromatism of the number dot (two), and bordered it with bright scarlet. He projected his chromatism into this circle. But the circle was, in fact, smaller than his chromatic circle, and a ring of orange was made by the superposition of the subjective yellow of his chromatism upon the objective scarlet. I enlarged the circle. This time he saw a white ring between the objective frame of scarlet and the subjective yellow. At last we got the edges of the chromatism to touch precisely the edges of the white circle. We had found the exact size of the chromatism and could now measure it to a millimetre".

The foregoing passage will show how clearly defined these enten-cephalic percepts may be. It is sometimes possible also to show that they represent (as I should expect them to represent) a memory more complete and a perception more exact than the supraliminal self can command. Thus, Mr. Galton had already mentioned a case where a lady used her chromatisms to correct her spelling - the chromatism showing, say, whether or not there were two és in agreeable, and correcting her supraliminal picture of the word by the symbolic coloured equivalent of each successive letter which thus rose from a memory deeper in her being. In the discussion following Professor Gruber's report at the Congress, Mr. Galton mentioned Lepsius the Orientalist as having been similarly guided in philological investigation. And one of M. Gruber's subjects, a professional singer, when taught to analyse his own chromatisms, found that they corrected his ear in singing; so that if he sang a false note without detecting it by ear the accompanying patch of colour showed him his mistake.1

In the American Journal of Psychology for April 1900 (vol. xi. pp. 377-404), Mr. G. M. Whipple gives a report of detailed observations of his own on two cases of synæsthesiae, and remarks that investigators must be prepared not only for a considerable degree of variation between different individuals, but also for variation within the same individual. One of his subjects showed marked taste photisms, together with the still more unusual feature of phonisms to pain, pressure, and temperature.