THE PERCEPTION OF SPACE. (ll.) 193

remark. It may be observed of pain, however, that its size has to be reduced to that of the normal tactile size of the organ which is its seat. A finger with a felon on it, and the pulses of the arteries therein, both ' feel ' larger than we believe they really ' are '. It will have been noticed in the account given that when two sensorial space-impressions, believed to come from the same object, differ, then the one most interesting, practically or aesthetically, is judged to be the trice one. This law of interest holds throughout though a permanent interest, like that of touch, may resist a strong but fleeting one like that of pain, as in the case just given of the felon. (c) Their Identification and Summation. Now for the next step in our construction of real space : How are the various sense-spaces added together into a consolidated and unitary continuum ? For they are, in man at all events, incoherent at the start. When a dentist is excavating a small cavity in one of our teeth we feel the hard point of his instrument scraping, in various distinctly differing directions, a surface which seems to our sensibility immensely larger than the subsequent use of the mirror tells us it really is. And though the directions of the scraping differ so completely inter se, not one of them can be identified with the particular direction in the outer world to which it corresponds. The space of the tooth- sensibility forms thus a little world by itself, which can only become congruent with the real space-world by further ex- periences which shall alter its bulk, identify its directions, fuse its margins, and finally imbed it as a definite part within a definite whole. Even though every joint's rotations should be felt to vary inter se as so many differences of direction in a common room ; even though the same were true of diverse tracings on the skin, and of diverse tracings on the retina respectively, it would still not follow that feelings of direc- tion, on these different surfaces, are intuitively comparable among each other, or with the other directions yielded by the feelings of the semi-circular canals. It would not follow that we should immediately judge them all to subdivide a common and single objective space- world. If with the arms in an unnatural attitude we ' feel ' things, we are perplexed about their shape, size and position. Let the reader lie on his back with his arms stretched/ above his head, and it will astonish him to find how ill able he is to recognise the geometrical relations of objects placed within 13