5GO THE HUMAN BODY. 



guish them; some sub-sensation quality not rising definitely 

 into prominence in consciousness must be present, com- 

 parable to the upper partials determining the timbre of 

 a tone. The accuracy of the localizing power varies widely 

 in different skin regions and is measured by observing 

 the least distance wJiick-inust ,s^parM^BLJQLbiQct^ (as the 

 blunted points of a pair of compasses) in order that they 

 may be felt as two. The following table illustrates some 

 of the differences observed 



Tongue-tip l.lmm. (.04 inch) 



Palm side of last phalanx of linger 2.2 mm. (.08 inch) 



Red part of lips 4.4 mm. (.16 inch) 



Tip of nose 6.6mm. (.24 inch) 



Back ol second phalanx of finger 11.0 mm. (.44 inch) 



Heel 22.0mm. (.88 inch) 



Back of hand 30.8 mm. (1.23 inches) 



Forearm 39.6 mm. (1.58 inches) 



Sternum 44.0 mm. (1.76 inches) 



Back of neck 52.8 mm. (2.11 inches) 



Middle of back 66.0 mm. (2.64 inches) 



The localizing power is a little more acute across the long 

 axis of a limb than in it; and is better when the pressure 

 is only strong enough to just cause a distinct tactile sensa- 

 tion, than when it is more power- 



^ u l> ^ ^ s a ^ so VG1 T readily and 

 rapidly improvable by practice. 



It might be thought that this 

 localizing power depended directly 

 on nerve distribution; that each 

 touch-nerve had connection with 

 a special brain-centr^ at one end 

 (the excitation of which caused 

 a sensation with a characteristic 

 local sign), and at the other end 

 was distributed over a certain skin 

 area, and that the larger this 

 area the farther apart might two 

 points be and still give rise to only one sensation. If this 

 were so, however, the peripheral tactile areas (each being 

 determined by the anatomical distribution of a nerve-fibre) 



