Inheritance of Acquired Characters 243 
if not, how can they be explained? His reply is that the 
differences can all be accounted for on the theory of the 
inheritance of use, for it is evident that “these gradations 
in tactile perceptiveness correspond with the gradations in 
the tactual exercise of the parts.’ Except from contact 
with the clothing the body receives hardly any touch sen- 
sations from outside, and this accounts for its small power 
of discrimination. The greater sensitiveness of the chest 
and abdomen, as compared with the back, is due to these 
regions being more frequently touched by the hands, and 
is also owing to inheritance from more remote ancestors, 
in which the lower surface of the body was more likely to 
have come in contact with foreign objects than was the back. 
The middle of the forearm and of the thigh are also less ex- 
posed than the knee and the hand, and have correspondingly 
the power of tactile discrimination less well developed. 
Weber showed that the tip of the tongue is more sensitive 
than any other part of the body, for it can distinguish be- 
tween two points only one twenty-fourth of an inch apart. 
Obviously, Spencer says, natural selection cannot account 
for such extreme delicacy of touch, because, even if it were 
useful for the tongue to distinguish objects by touch, this 
power could never be of vital importance to the animal. It 
cannot even be supposed that such delicacy is necessary for 
the power of speech. 
The sensitiveness of the tongue can be accounted. for, c 
however, Spencer claims, as the result of the constant use 
of the tongue in exploring the cavity of the mouth. It is 
continually moving about, and touching now one part, and 
now another, of the mouth cavity. “No advantage is gained. 
It is simply that the tongue’s position renders perpetual ex- 
ploration almost inevitable.” No other explanation of the 
facts seemed possible to Spencer. 
Two questions will at once suggest themselves. First, can 
it be shown that the sensitiveness to touch in various parts of 
