THE PERCEPTION OF SPACE. ^Qo 



every sense, experience takes ah initio the spatial form. We 

 have also sliown that in the cases of the retina and skin 



other parts at all, the relation must be in the line itself, — for the line and 

 the parts are the only things supposed to be in consciousness. And we can 

 furthermore suggest a reason why parts appearing thus in relation to each 

 other in a line should fall into an immutable order, and each within that 

 order keep its characteristic place. 



If a lot of such local signs all have any quality which evenly augments 

 as we pass from one to the other, we can arrange them in an ideal serial 

 order, in which any one local sign must lie below those with more, above 

 those with less, of the quality in question. It must divide the series into 

 two parts, — unless indeed it have a maximum or minimum of the quality, 

 ■when it either begins or ends it. 



Such an ideal series of local signs in the mind is, however, not yet iden- 

 tical with the feeling of a line in space. Touch a dozen points on the skin 

 successively, and there seems no necessary reason why the notion of a defi- 

 nite line should emerge, even though we be strongly aware of a gradation 

 of quality among the touches. We may of course symbolically arrange 

 them in a line in our thought, but we can always distinguish between a 

 line symbolically thought and a line directly felt. 



But note now the peculiarity of the nerve-processes of all these local 

 signs: though they may give no line when excited successively, when ex- 

 cited together they do give the actual sensation of a line in space. The 

 sum of them is the neural process of that line; the sum of their feelings 

 is the feeling of that line; and if we begin to single out particular points 

 from the line, and notice them by their rank, it is impossible to see how 

 this rank can appear except as an actual fixed space-position sensibly felt 

 as a bit of the total line. The scale itself appearing as a line, rank in it 

 must appear as a definite part of the line. If the seven notes of an octave, 

 •when heard together, appeared to the sense of hearing as an outspread 

 line of sound — which it is needless to say they do not — why then no one 

 note could be discriminated without being localized, according to its pitch, 

 in the line, either as one of its extremities or as some part between. 



But not alone the gradation of their quality arranges the local-sign 

 feelings in a scale. Our movements arrange them also in a fowe-scale. 

 Whenever a stimulus passes from point a of the skin or retina to point/, 

 it awakens the local sign feelings in the perfectly definite time-order abcdef. 

 It cannot excite/ imtil cde have been successively aroused. The feeling c 

 sometimes is preceded by ab. sometimes followed by ba, according to the 

 movement's direction; the result of it all being that we never feel either a, 

 c, or/, without there clinging to it faint reverberations of the various time- 

 orders of transition in which, throughout past experience, it has been 

 aroused. To the local sign a there clings the tinge or tone, the penumbra 

 or fringe, of the transition bed. To/, to c, there cling quite different tones. 

 Once admit the principle that a feeling may be tinged by the reproductive 

 consciousness of an habitual transition, even when the transition is not 

 made, and it seems entirely natural to admit that, if the transition be habit- 

 ually in the order abcdef, and if a, c, and/ be felt separately at all, a will 

 be felt with an essential earliness, /with an essential lateness, and that c wiU 



