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 THE PEKCEPTION OF SPACE. (ll.) 201 successive points of its path by incoming sensations pro- duced by the slipping over each other of the cartilages on which it turns ; and the whole phenomenon, instead of re- futing, most brilliantly corroborates the view that localisa- tion is exclusively a surface-affair. Muscular contraction is only indirectly instrumental in giving us space -feelings, ~by its objective effects on surfaces. In the case of skin and retina, it produces a motion of the stimulus upon the sur- face; in the case of joints it produces a motion of the surfaces upon each other such motion being by far the most deli- cate manner of sensibly exciting the surfaces in question. One is tempted to doubt whether the muscular sensibility as such plays even a subordinate part as sign, of these more immediately geometrical perceptions which are so uniformly associated with it as effects of a common cause the contrac- tion objectively considered. 1 1 The admirably judicious A. W. Volkmann says ( Untersuchungen im Gebiete der Optik, Leipzig, 1863, p. 188): "Muscular feeling gives tolerably fine evidence as to the existence of movement, but hardly any direct infor- mation about its extent or direction. We are not aware that the contrac- tions of a supinator longus have a wider range than those of a supinator brevis ; and that the fibres of a bipenniform muscle contract in opposite directions is a fact of which the muscular feeling itself gives not the slightest intimation. Muscle-feeling belongs to that class of general sensa- tions which tell us of our inner states, but not of outer relations; it does not belong among the space-perceiving senses." See also Ibid., p. 189, and Hering, Beitrcige, pp. 31, 240. Weber (Article "Tastsinn") also calls attention to the fact that muscular movements as large and strong as those of the diaphragnl go on continually without our perceiving them as motion. See also Lewes, Problems, vol. ii., p. 478. But the final crushing defeat of the muscular-sense as the chief agent in space-perception is given by Prof. Lipps in a few pages (6 to 27 of his Psychologische Studien, 1885), which I advise all students to read. Nevertheless certain facts may still be brought up against our surface- theory. When we move the wings of the nostrils, the external ear and, to a certain degree, the tongue, the feeling we get is distinctly one of move- ment, but it involves anatomically no such passage of anything over a surface as, according to our text, it should. The explanation is that we have learned the movement-significance of these movement-feelings and skin-stretchings, by producing them "passively," by manipulating the parts on former occasions with our fingers. A personal experience, made since the text was written, seems to me strongly to corroborate this view. For years I have been familiar, during the act of gaping, with a large, round, smooth sensation in the region of the throat, a sensation characteristic of gaping and nothing else, but which, although I had often wondered about it, never suggested to my mind the motion of anything. The reader pro- bably knows from his own experience exactly what feeling I mean. It was not till one of my students told me, that I learned its objective cause. If we look into the mirror while gaping, we see that at the moment we have this feeling, the uvula or hanging palate rises by the contraction of its intrinsic muscles. The contraction of these muscles and the com-