68 THE THEORY OF NATURAL SELECTION 
that in a savage, since the sense of touch is the only 
one with which his back is provided, it might be 
useful for that surface to have acquired a more deli- 
cate sense of touch than the anterior surface, which 
is guarded by the power of vision, as well as being 
more readily explored by the sensitive finger-tips. 
If such an argument is regarded as far-fetched, so in 
an equal degree must be any attempt to explain the 
actually observed distribution through the action of 
natural selection. 
On the other hand; Spencer points out that the 
series of parts enumerated in the above table stands 
in almost exactly the order of the frequency with 
which the members composing it are actually exposed 
to tactual experience. 
The tongue is perpetually in contact with the minute 
unevennesses afforded by the surfaces of the teeth. 
The palm of the hand and the lower joints of the 
fingers are used chiefly in grasping, and not in the 
more minute manipulations for which the finger-tips 
are employed. And the experience of the back of the 
hand in coming into contact with various irregular 
bodies is not to be compared with that of the palmar 
surface, yet it is very much greater than that of so 
unexposed a part as the middle of the forearm. 
For the carrying on of his argument, Herbert Spencer 
has shown that increased use of the power of dis- 
criminating small objects by touch is accompanied by 
an increased degree of sensitiveness in individuals. 
Blind people use their finger-tips in this way to a much 
greater extent than those whose sight is unimpaired. 
