TOUCH. 127 



in order to discover the quality of the body thus applied. 

 This effort is nothing but the stretching of the nervous papillae, 

 that they may enlarge the field of contact with the body under 

 examination. 



The pleasure or pain produced by the sense of touch, de- 

 pends chiefly upon the friction, or number of impulses, made 

 upon the papillae. Embrace any agreeable body with your 

 hand, arid allow it to remain perfectly at rest, and you will 

 find the pleasure not half so exquisite as when the hand is 

 gently moved backward and forward upon the surface. Apply 

 the hand to a piece of velvet, and it is merely agreeable; run 

 the hand repeatedly on the surface of the cloth, and the 

 pleasant feeling will be augmented in proportion to the num- 

 ber of impulses on the papillae. When a man is pinched 

 with hunger, the sight or idea of palatable food raises the 

 whole papillae of his tongue and stomach. From this circum- 

 stance he is highly regaled by eating. But if he eats the 

 same species of food when his stomach is less keen, the pleas- 

 ure in the one case is not to be compared with what is felt in 

 the other. The cause is obvious; his desire was not so ur- 

 gent ; the object, of course, was less alluring ; and therefore 

 he was more remiss in erecting his papillae, or in putting them 

 in a tone suited to such eminent gratification. 



The same observations are applicable to disagreeable or 

 painful objects of contact. If the hand is laid upon a gritty 

 stone, or a piece of rusty iron, the feeling is disagreeable ; 

 but if it is frequently rubbed upon the surface of these bodies 

 the feeling becomes insufferably irksome. 



It is by the sense of touch, that men and other animals are 

 enabled to perceive and determine many qualities of external 

 bodies. By this sense we acquire the ideas of hardness and 

 softness, of roughness and smoothness, of heat and cold, of 

 pressure and weight, of figure and of distance. The sense of 

 touch is more uniform, and liable to fewer deceptions, than 

 those of smelling, tasting, hearing, and seeing ; because, in 

 examining the qualities of objects, the bodies themselves must 

 be brought into actual contact with the organ, without the 

 intervention of any medium, the variations of which might 

 mislead the judgment. 



' The accuracy of this sense is much improved by habit ; 

 and in some cases where the senses of sight or hearing have 

 been injured, this has acquired so great a degree of sensibil- 

 ity, as in a measure to supply their loss. Thus, blind men 

 ,. are sometimes able to distinguish the qualities of objects with 



