THE SENSE OF TOUCH. 709 



with cork, and in ascertaining how close the points of the 

 compasses might be brought to each other, and still be 

 felt as two bodies. He examined in this manner nearly 

 every part of the surface of the body, and has given tables 

 showing the relative degrees of sensibility of different 

 parts. Experiments of a similar kind have been per- 

 formed also by Valentin : and, among the numerous 

 results obtained by both these investigators, it appears 

 that the extremity of the third finger, and the point of the 

 tongue are the parts most sensitive : a distance of as little 

 as half a line being here distinguished. Next in sensitive- 

 ness to these is the mucous surface of the lips, which can 

 perceive the two points of the compass when separated to 

 the distance of about a line and a half : on the dorsum of 

 the tongue they require to be separated two lines. The 

 parts in which the sense of touch is least acute are the 

 neck, the middle of the back, the middle of the arm, and. 

 the middle of the thigh, on which the points of the com- 

 pass have to be separated to the distance of thirty lines to 

 be perceived as distinct points (Weber). Other parts of 

 the body possess various degrees of sensibility intermediate 

 between the above extremes. 



A sensation in a part endowed with touch appears to 

 the mind to be, cateris paribus, more intense when it is 

 excited in a large extent of surface than when it is con- 

 fined to a small space. The temperature of water into 

 which he dipped his whole hand, appeared to Weber to be 

 higher than that of water of really higher temperature, 

 in which he immersed only one finger of the other hand. 

 Similar observations may be made by persons bathing in 

 warm or cold water. 



Part of the ideas which we obtain of the conditions of 

 external bodies is derived through the peculiar sensibility 

 with which muscles are endowed the sensibility by which 

 we are made acquainted with their position, and the degree 

 of their contraction. By this sensation, we are enabled to 



