THE SENSE OF FEELING. 261 



change of position of the limbs, a sensation of definite quality and intensity is 

 connected, and hence, when experience is sufficiently matured, involuntarily 

 associates with every such sensation a correct idea of the nature and extent of 

 the corresponding movement. How, now, do those sensations of movement 

 co-operate with the sensations of touch in the formation of objective ideas ? Wo 

 experience that one and the same movement, of the hand, for instance, and 

 therefore one and the same feeling of movement is at one time connected with 

 a sensation' of touch, and at another is not, (according as some external object is 

 or is not encountered,) and we thence conclude, in the first place, that the sen- 

 sation of touch is no essentially concomitant phenomenon, no invariable conse- 

 quence of the sensation of movement. Wo further experience that often, in the 

 conscious and entire rest of our limbs, a sensation of touch arises, (if an object 

 be brought into contact with our organs of touch,) that the state of rest still 

 continuing, the sensation changes, and difierent organs of touch became succes- 

 sively sensitive, (if the object be moved along the surfaces of this species of sen- 

 sibility.) We experience, finally, that if by a movement a sensation of touch 

 commences, the same becomes changed, on further movement, in various ways, 

 both qualitative and quantitative. It is evident that all these experiences must 

 force upon us the inference that the causes of our sensations of touch are ex- 

 ternal ; that the movement of the limbs brings our organs of touch into commu- 

 nication with difierent outward excitants of sensation. From these external ob- 

 jects of touch we learn to distinguish, as belonging to our own body, those whose 

 touch produces a double sensation, as well in the part touching as in that which 

 is touched. If a part of our body be insensible, it seems to the touching finger, 

 provided no other sense correct the illusion, to be a foreign and external object. 

 Thus it often happens that through protracted pressure in sleep on the nerves 

 of the arm, the latter is rendered, for a time, so entirely insensible that when, on 

 awaking, the arm which is "asleep" is touched with the hand of the other, we 

 can scarcely but believe that it is the arm of a stranger with which our hand 

 has come into contact. 



Finally, we might here adduce an important general distinction between the 

 sense of touch and of pain, drawn from the relations of both to the exciting cause. 

 How sensitive an apparatus of measurement as regards pressure and temperature, 

 is our organ of touch ; what small degrees of pressure, what slight changes of tem- 

 peratui-e does it indicate ! Not that, like the thermometer and barometer, it an- 

 nounces the absolute amount of the weight pressing upon the skin, or of the tem- 

 perature of a medium to which it is exposed; but it informs us by sensations, to 

 which we can assign no numerical value, whether the skin is compressed or 

 stretched, whether heat be supplied or withdrawn, and the perfection of its per- 

 formances rests chiefly on this, that of two pressures or temperatures taking 

 effect one after the other on the skin, it can rightly discriminate the higher and 

 lower, even to slight difi'erences. How exactly, besides, does the duration of 

 a sensation of touch correspond with the duration of the exciting cause; it has, 

 indeed, been observed that the sensation does really endure for a minute point 

 of time longer than, for instance, the actual compression of the skin, but the 

 duration of this excess is so inappreciably small as not to detract sensibly from 

 the exact synchronism of the touch and the sensation. If we pass a finger 

 rapidly over sandstone, we distinctly feel that the surface is rough and beset 

 with prominences, and why ? Because we are able to distinguish the alternation 

 of impressions caused by the minute projections and the pauses in those sensations 

 produced by the intervening depressions, however short these pauses may be 

 rendered by rapidity of movement. How dift'erent is it in these respects with 

 the common feeling of pain. In the first place, for its excitation, proportiouably 

 far higher degrees of external influence are requisite; at the same points of tho 

 skin where the slightest pressure or the least alternations of heat and cold are 



