THE SPECIAL SENSES 227 
sense, or the sense of touch. The special organs of this 
sense are usually simple hairs or papille connecting with a 
nerve. These tactile hairs or papille may be distributed 
pretty evenly over most of the body, or may be mainly con- 
centrated upon certain parts in crowded groups. Many of 
the lower animals have projecting parts, like the feeling 
tentacles of many marine invertebrates, or the antenne 
(feelers) of crabs and insects, which are the special seat 
of the tactile organs. Among the vertebrates the tactile 
organs are either like those of the invertebrates, or are 
little sac-like bodies of connective tissue in which the 
end of a nerve is curiously folded and convoluted (Fig. 
141). These little touch corpuscles simply lie in the cell 
layer of the skin, covered over thinly by the cuticle. Some- 
times they are simply free, branched 
nerve-endings in the skin. These 
tactile corpuscles or free nerve-end- 
ings are especially abundant in those 
parts of the body which can be best 
used for feeling. In man the fin- 
ger-tips are thus especially supplied ; 
in certain tailed monkeys the tip of 
the tail, and in hogs the end of the 
snout. The difference in abundance 
of these tactile corpuscles of the skin 
can be readily shown by experiment. 
With a pair of compasses, whose M16, ‘41 Tactile papilla of 
points have been slightly blunted, after Kozuuxer. 
touch the skin of the forearm of a 
person who has his eyes shut, with the points about three 
inches apart and in the direction of the length of the arm. 
The person touched will feel the points as two. Repeat 
the touching several times, gradually lessening the dis- 
tance between the points. When the points are not more 
than an inch to an inch and a half apart, the person 
touched will feel but a single touch—that is, the touching 
