270 ON THE SENSES. 



these are we originally endowed with the possibility of associating ideas of place 

 with the sensation of touch, but we do not thence derive the ideas themselves. 

 The child at first receives only the impressions differently toned according to 

 the place of the excitation ; it gradually learns by circuitous means that the sen- 

 sation is qualified by the place from which the excitation proceeds, and that a 

 particular point in the skin corresponds to each particular token. The interpre- 

 tation of these local tokens is the result of the joint and reciprocal self-training of 

 the sduse of sight, the sense of touch, and the muscular sense, by which last is 

 meant the feeling of effort in the miiscles moving the limbf, a feeling whose in- 

 valuable services, as regards the point iu question, wc have before had occasion to 

 signalize. Were the organs of touch not movable in themselves and iu relation to 

 one another, and were their movements not accompanied by this muscular feeling, 

 we should be destitute of one of our most imporlant sources of information, and 

 scarcely in a condition, as we actually are, to judge accurately in regard to the 

 performances of our organ of touch. If with the finger of one hand we touch 

 a point in the palm, for instance, of the other, there arises a feeling in the touch- 

 ing part as well as in that touched, each feeling being attended by the local token 

 appropriate to itself; if we touch with the same finger another point of the palm, 

 the local token in the part touched will be a different one. If we move the 

 finger gradually over the palm we receive a continuous series of sensations with 

 different tokens. It is not alone that we see the course described by the finger; 

 we know its extent and direction also from the feelings generated by the moving 

 muscles, and we thus arrive at the idea that tlie sensations with the distinctive 

 local tokens belong to distinct but contiguous points of the skin, while the form 

 of the movement, whether in a right line or a circle, is made known to us 

 by this same muscular feeling. Thus by long and attentive study the mind is 

 qualified rightly to interpret each local token, and, in the case of two simulta- 

 neous impressions, to judge correctly of the relative situation and distance of 

 the two corresponding points of the skin ; whence the whole cuticle may be 

 conceived of as a mosaic of sensitive points, in which wc have learned to dis- 

 tinguish each point by its characteristic coloring, and to refer with the rapidity 

 of intuition each local token to its definite place within the general outline. 



It results from what has been said, that while two simultaneous impressions 

 on the skin, v^hen the sensations convey different local tokens, give rise to the 

 idea of two different local excitations, the mind will, on the other hand, neces- 

 sarily refer both impressions to one place when the tokens are alike, and hence 

 the resulting sensation will be single. We have further supposed that each 

 different nerve determines a different shade of sensation, whence it follows that 

 the sensation occasioned by each fibre conveys the idea of that point of the skin 

 in which the fibre terminates, and that hence pressure at the points, Avhose com- 

 pression stimulates one and the same fibre, will generate only one and the same 

 perception of place. This is a supposition which we must here submit to a closer 

 examination. That one and the same fibre cannot simultaneously convey to the 

 brain two currents of different quality, or with different local tokens, and that 

 lience two sensations cannot be generated at the same time through the same 

 fibre, is a physiological law, which we must request the reader to take for 

 granted, as its demonstration here would lead us into too wide a digression. 

 Another question, however, is, whether in reality each fibre imprints on the sen- 

 sation a separate stamp ; whether, because two different fibres are simultaneously 

 excited, therefore, the double sensation is necessarily accompanied with a conscious 

 separation of the impressions. Every one knows that thei'e is not the smallest 

 portion in the whole surface of the skin which is not sensitive, and which, if 

 touched with the point of a needle, will not yield a sensation. But each point, 

 though sensitive, is not endowed with its own nerve ; on the contrary, the mi- 

 croscope shows us that the papillce in which the nerves terminate are separated 



