DISCRIMINATION BY TOUCH 67 
that with the tip of the forefinger the points can be 
distinctly recognised as two when they are separated 
by no more than j, inch. When applied to the middle 
of the back, on the other hand, the points must be 
opened to a distance of 24 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: “ ‘ie -» gy inch. 
Tip of finger. . : ae 55 
Inner surface of second ‘joint of 
finger .. i os a ery 
Tip of nose .. 4 oss 
Cheek, palm of hand, and end of 
great-toe 4 54 
Forehead .. we: OE ay 
Back of hand, crown of head ee i Ap 
Breast Id ons 
Middle of back, middle of thigh, 
middle of forearm aa 2k; 
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 
5—2 
