942 CUTANEOUS SENSATIONS. 



environmental objects, that is, we project them. The force with which 

 the quality inheres is different in different senses. Visual perceptions 

 seem almost unconquerably the properties of objects in space round 

 about. Among the cutaneous senses, touch is that one most possessed 

 of objectivity. When an external object is touched by or touches the 

 finger, there arises, as an immediate rather than as really a mediate 

 result, a presentation of a something not " I," endowed with quality, 

 "hard," soft," "smooth," etc. Complete emancipation from the in- 

 voluntary " projection " is not possible for us. In some cases the degree 

 of projection of touch is very marked. Thus the perceptions of touch 

 evoked by contact of objects with hairs are referred to the insentient 

 free portions of the hairs themselves, even to their very tips. Similarly 

 with the teeth. Again, the surgeon, as far as touch is concerned, 

 actually lengthens his fingers by using a probe ; a rod pressed by the 

 fingers by one end upon a yielding or hard object gives two sensations, 

 one to the fingers where it meets them, and a second referred to the 

 point of contact of the rod with it. In this we have a germ of the 

 projicience so marked in visual sense of space. 1 



That identical muscular sensations may be accompanied by non- 

 identical cutaneous, is probably a main factor in giving the latter 

 " objectivity." In all movements that involve the cutaneous surface, 

 that surface being a sensifacient one, if those movements occasion 

 adequate stimulation of the surface, cutaneous sensations will be 

 generated in addition to the muscular sensation inherent in the move- 

 ment. The two senses together will react to an object in greater range 

 of quality than will either alone ; the two will obtain more criteria for 

 judging the object than will either one ; the two are alike endowed pre- 

 eminently with "local sign," and "projection" is an adjunct of the 

 intuition or perception of space. When different objects or one object 

 under different circumstances, evoke sensations, tactual and muscular, 

 which vary (as to extension, intensity, and especially " local sign ") not 

 harmoniously, but in almost infinite combination, the compound percep- 

 tions resulting form a store of data especially favourable for the judging 

 of space. The very variety of the variously congruent combinations of 

 muscular sense and touch, the irregular flux of correspondence and of 

 non-correspondence between the two, comes to imbue the perceptions of 

 the latter with projection. 



In the retina the extension of the sensifacient surface in space is 

 such as to preclude in the same individual any one retinal point ever 

 supplying the adequate stimulus to any other, i.e. no part of the two 

 retinae can be seen by any other part. With the skin it is different. 

 One part of its surface may supply adequate stimuli to other parts, 

 and often does. A very small fraction only of the human surface 

 is inaccessible to touch by the individual's own hand. It results 

 thence that we regard the cutaneous sensifacient surface although it, 

 like the retina, belongs to the sentient " self " as, relatively to that, an 

 external thing, and come to endow it, as we endow other objects of the 

 environment, with the qualities of our sensations. Thus on this, the 

 so-called " double touch," is built, so to say, a bridge from " outside of 

 me" to "me" and "self." Hence tactual and the thermal cutaneous 

 sensations, although " projected," are less so than are visual. 



Illusions in tactual judgments of space. Two " touches " a certain 

 1 E. H. Weber, loc. ciL 



