THE SENSE OF FEELING. 27 1 



from one auotlier by a greater or less number of papillse which are devoid of 

 nerves, so that in many parts of the skin there exists quite a considerable inter- 

 val between the ends of these fibres. With this anatomical fact, however, it is 

 easy to reconcile the further fact that even those points of the epidermis, situated 

 over a portion of the cutis which is destitute of nerves, should be perfectly sen- 

 sitive. In order that the pressure produced, for instance, by a needle's point 

 should stimulate the end of a nerve, it must necessarily be propagated through 

 the whole thickness of the integument under which the nerves occur. This 

 propagation of the pressure will not take place in a perpendicular direction only, 

 but will also extend laterally so as to involve to a certain degree the particles of 

 the skin in proximity with those directly compressed. Just as a circular wave 

 spreads in the water, when the fall of a stone disturbs however small a part of the 

 surface, does there arise in the skin, from the pressui'e of the needle, a propagated 

 motion which affects the particles within a certain circuit, and not merely in a 

 perpendicular line. However light the touch or minute the instrument, the wave, 

 if so we may call it, in the skin is always wide enough to reach the end of a 

 nerve, even in parts where the nerves are most sparingly distributed. But the 

 microscope further shows us that a special fibre is not appropriated to each 

 separate extremity of a nerve, but that frequently the same fibre is divided close 

 under the skin into several branches, so that in many places a greater or less 

 extent of the surface (of a line, for instance, in diameter) is supplied with these 

 nerve-extremities by a single fibred From which it follows, of course, that 

 within this extent each single point will be sensitive, and yet if, within that 

 circuit, we press simultaneously upon two separate points, the two impressions 

 can produce but one simple sensation, since, however distinct the extremities 

 of the nerve, the impressions act as an excitant only upon one fibre communi- 

 cating with the brain, and do not, as in the case of a double sensation, convey 

 through their local tokens the idea of two distinct points of contact. 



Few, probably, of my reaaers have so nicely tested their organ of touch as to 

 have acquired the knowledge that under certain conditions two simultaneous 

 impressions on the skin produce but one simple sensation ; that the touch of 

 two points, for instance, may seem but a single touch, when the sense of sight 

 does not betray us into the belief of a twofold sensation by disclosing its two- 

 fold origin. A simple and easily repeated experiment will strikingly confirm 

 the truth of this proposition. Let the eyes of any one, who is not previously 

 advised of what is intended, be carefully bandaged, in order that there may be 

 no such betrayal of the judgment as that we have just spoken of; then let a 

 common but blunt pair of compasses, opened to the extent of half an inch, be 

 applied to the back of the hand of the person upon whom the experiment is 

 tried, care being taken that both points shall touch the skin at exactly the same 

 time. If we now ask the person in question whether the impression be single 

 or double, we shall with certainty receive the assurance that it is a single one. 

 Place the points of the compasses, with the same extension, iipon the skin of 

 the finger's end, and the subject of experiment will immediately and correctly 

 inform us that the impression is double. If the points be applied to the skin of 

 the back, we may separate them to the extent of even two inches without 

 causing the sensation of a double pressure, provided the judgment is unbiassed 

 and the subject carefully considers the nature of his sensation. Next, let the com- 

 passes, with the points separated to the distance of ^ inch and placed perpendicu- 

 larly to one another, be applied just in front of one ear ; the subject will again be 

 conscious of only a single impression. Now move both points, still preserving the 

 same distance from one another and in constant contact with the skin, across the 

 face as far as the other ear ; at a certain place in the transit the single sensation 

 will be felt to change into a double sensation ; as the points approach the mouth it 

 will seem that they are gradually separating further from one another, and when 



