It4 THE PHILOSOPHY 



been able to diftinguifli objed^s with fuch accuracy as at pre- 

 fent it is capable of performing. When an iniipicl body, 

 or a body which conveys but a very feeble fenfation of tafte, 

 is applied to the tongue, we are confcious of an eftbrt which 

 that organ makes in order to difcover the quality of the body 

 thus applied. This effort is nothing but the ftretching of 

 the nervous papillae, that they may enlarge th^ field of con- 

 tacft with the body under examination. 



The pleafure or pain produced by the fenfe of touch de- 

 pends chiefly on the fridtion, or number of impulfes, made 

 upon the papillae. Embrace any agreeable body with your 

 hand, and allov/ it to remain perfectly at refl:, and you will 

 find the pleafure not half fo exquifite as when the hand is 

 gently moved backward and forward upon the furface. Ap- 

 ply the hand to a piece of velvet, and it is merely agreeable : 

 Rub the hand repeatedly on the furface of the cloth, and 

 the pleafant feeling will be augmented in proportion to the 

 number of impulfes on the papillae. When a man is pinch^ 

 ed with hunger, the fight or idea of palatable food raifes the 

 whole papillae of his tongue and ftomach. From this cir- 

 cumftance he is highly regaled by eating. But, if he eats 

 the fame fpecies of food when the flomach is lefs keen, 

 the pleafure in the one cafe is not to be compared with what 

 is felt in the othpr. The caufe is obvious : His defire was 

 not fo urgent •, the obje6V, of courfe, was lefs alluring \ and 

 therefore he was more remifs in eredling his papillae, or in 

 putting theni in a tone fuited to fuch eminent gratification. 



The fame obfervations are applicable to difagreeable or 

 painful objecls of contadl. If the hand is laid upon a gritty 

 ftone, or a piece of rufty iron, the feeling is difagreeable v 

 but if it is frequently rubbed upon the furface of thefe bodies, 

 the feeling becomes infufFerably irkfome. 



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

 are enabled to perceive and determine many qualities of ex- 



