242 Evolution and Adaptation 
only one-twelfth of an inch apart, and if the points are moved 
nearer together, they give the sensation of only one point. 
The inner surfaces of the second joints of the fingers can 
only distinguish two points when they are one-sixth of an 
inch apart. The innermost joints are less discriminating, 
and are about equal in the power of discrimination to the tip 
of the nose. The end of the big toe, the palm of the hand, 
and the cheek discriminate only about one-fifth as well as do 
the tips of the fingers. The back of the hand and the top 
of the head distinguish only about one-fifteenth as well as 
the finger-tips. The front of the thigh, near the knee, is 
somewhat less sensitive than the back of the hand. On the 
breast the points of the compasses must be separated by more 
than an inch and a half in order to give two sensations. In 
the middle of the back the points must be separated by two 
and a half inches, or more, in order to give two separate 
impressions. 
What is the meaning of these differences, Spencer asks. 
If natural selection has brought about the result, then it must 
be shown that “these degrees of endowment have advan- 
taged the possessor to such an extent that not infrequently 
life has been directly or indirectly preserved by it.” He 
asks if this, or anything approaching this, result could have 
occurred. 
That the superior perceptiveness of the forefinger-tip 
might have arisen through selection is admitted by Spencer, 
but how could this have been the case, he asks, for the mid- 
dle of the back, and for the face? The tip of the nose has 
three times more power of discrimination than the lower 
part of the forehead. Why should the front of the thigh 
near the knee be twice as perceptive as in the middle of 
the thigh; and why should the middle of the back and of 
the neck and the middle of the forearm and of the thigh 
stand at such low levels? Is it possible, Spencer asks again, 
that natural selection has determined these relations, and 
