DISCRIMINATION BY TOUCH 61 



that with the tip of the forefinger the points can be 

 distinctly recognised as two when they are separated 

 by no more than T V inch. When applied to the middle 

 of the back, on the other hand, the points must be 

 opened to a distance of 2^ inches before the sensation 

 of a single touch becomes resolved into two distinct 

 sensations. 



The distribution of this power of discrimination over 

 the surface of the body is approximately as follows : 



Tip of tongue . . . . -si inch. 



Tip of finger.. .. .. . . 1J_ ,, 



Inner surface of second joint of 



finger & 



Tip of nose . . . . . . . . 



Cheek, palm of hand, and end of 



great -toe | 



Forehead . . . . . . . . f- ,, 



Back of hand, crown of head . . i 



Breast . . . . . . . . i ,, 



Middle of back, middle of thigh, 



middle of forearm . . , . 2$ 



Now, it is out of the question to suppose that natural 

 selection can account for all these differences. An 

 increased sensitiveness of the tips of the fingers might, 

 indeed, be of so much use as to give the individual 

 possessing it a definitely increased chance of survival. 

 But it is hard to believe that it can be important for 

 a man to have the tip of his tongue twice as sensitive 

 as the tips of his fingers. And why should the tip of 

 the nose be more sensitive than the cheek, or the 

 cheek than the top of the head, or the breast than 

 the back ? In the last case it might even be suggested 



