Dr Graves oji the Sense of Touch, 78 



perceiving painful or pleasing impressions, is much more gene- 

 rally diffused, and is the result of a much simpler organiza* 

 tion. In fact, although the internal, mucous, fibrous, and serous 

 surfaces, and the parenchyma of the different organs, are all 

 capable of becoming actually painful, particularly when inflamed, 

 yet it is very doubtful whether the sense of touch, properly so 

 called, is ever exercised by those parts. No foreign substance 

 is ever distinctly felt by the touch in the stomach and bowels ; 

 a sensation, painful or pleasing, is indeed excited by some mat- 

 ters immediately after they are swallowed, but all consciousness 

 of their presence, by means of the sense of touch, soon ceases, 

 and it cannot be again recalled by the utmost exertion of the will. 

 A foreign substance lodged in the alimentary canal, or in the 

 trachea, may give rise to the greatest possible degree of irrita- 

 tion ; but though it thus acts upon the nerves of the parts im- 

 mediately in contact with it, these nerves convey no idea to the 

 sufferer of the shape or size of the body, or of any other of its 

 physical qualities, concerning which we receive information 

 through the medium of the sense of touch. 



Webef s observations (pp. 67, 77) on the comparative tactile 

 energy of the different portions of the trunk of the body, are 

 extremely curious, and have disclosed a very remarkable diffe- 

 rence between the sense of touch in the trunk and in the extre- 

 mities. In the latter, where the points of the compass are placed 

 across the axis of the limb horizontally, they are much more 

 accurately distinguished than when they are placed in the longi- 

 tudinal direction, or parallel to the axis of the limb (vertical), in 

 other words, the limit of' confusion is much sooner attained in 

 the vertical than in the horizontal position of the points. Now, 

 in many parts of the trunk the contrary obtains, and the verti- 

 cal position is more accurate than the horizontal ; this singular 

 difference Weber explains by the different manners in which the 

 nerves supplying the extremities and the trunk are distributed. 

 The branches of the former generally run nearly parallel to the 

 axis, while those of the latter pursue in most cases a transverse 

 course ; all parts of the trunk do not exhibit this difference. 

 Whether this explanation is or is not admitted, the fact is un- 

 doubted. Our author next proceeds to shew what* motion, 

 whether it be of the touching organ or of the body to be touch- 

 ed, greatly augments the clearness and accuracy of the percep- 



