THE PERCEPTION OF SPACE. 159 



cal cause. It will be tinged hy the gastric local sign, and 

 the nerve-ceutre supporting this latter feeling will excite 

 the centre supporting the dermal and muscular feelings 

 habitually associated with it when the excitement was 

 mechanical. From the combination the same peculiar 

 ■vastness will again arise. In a word, ' something ' in the 

 stomach-sensation * reminds ' us of a total space, of which 

 the diaphragmatic and epigastric sensations also form a 

 part, or, to express it more briefly still, suggests the neigh- 

 borhood of these latter organs.* 



Revert to the case of two excited points on a surface with 

 an unexcited space between them. The general result of 

 previous experience has been that when either point was 

 impressed by an outward object, the same object also 

 touched the immediately neighboring jDarts. Each point, 

 together with its local sign, is thus associated with a circle 

 of surrounding points, the association fading in strength as 

 the circle grows larger. Each will revive its own circle ; 

 but when both are excited together, the strongest revival 

 will be that due to the combined irradiation. Now the tract 

 joining the two excited points is the only part common to the 

 two circles. And the feelings of this whole tract will there- 

 fore awaken with considerable vividness in the imagination 

 when its extremities are touched by an outward irritant. 

 The mind receives with the impression of the two distinct 

 points the vague idea of a line. The twoness of the points 

 comes from the contrast of their local signs : the line comes 

 from the associations into which experience has wrought 

 these latter. If no ideal line arises we have duality with- 

 out sense of interval ; if the line be excited actually rather 



* Maybe the localization of intracranial pain is itself due to such asso- 

 ciatiou as this of local signs with each other, rather than to their qualita- 

 tive similarity in neighboring parts (supra, p. 19); though it is conceivable 

 that association and similarity itself should here have one and the same 

 neural basis. If we suppose the sensory nerves from those parts of the 

 body beneath any patch of skin to terminate in the same sensorial brain- 

 tract as those from the skin itself, and if the excitement of any one fibre 

 tends to irradiate through the whole of that tract, the feelings of all fibres 

 going to that tract would presumably both have a similar intrinsic quality, 

 and at the same time tend each to arouse the other. Since the same nerve- 

 trunk in most cases supplies the skin and the parts beneath, the anatomical 

 hypothesis presents nothing improbable. 



