390 TAOTILE SENSIBILITY OF THE SKIN. 
Sense of Touch. ao 
490. By the sense of Touch is usually understood that — 
modification of the common sensibility (§ 487) of the body, of — 
which the surface of the skin is the especial seat. In some 
animals, as in Man, nearly the whole exterior of the body is — 
endowed with it in no inconsiderable degree ; but in others, — 
as in the larger number of Mammals, most Birds and Rep- 
tiles, and many Fishes, the greater part of the body is so 
covered by hairs, scales, or bony plates, as to be nearly insen- 
sible ; and the faculty is restricted to particular portions of 
the surface, which often possess it in a very high degree. 
The sensory impressions, by which we receive the sensation of 
Touch, are made by the objects themselves upon the nerves — 
which are distributed to the Skin; the general structure of — 
which has been already described (§$ 36—38). Of the papillae 
which are thickly set upon many parts of its surface, some — 
contain looped tufts of blood-vessels without nerves ; and as — 
these are found to be largest where the Epidermis is thickest — 
(as, for example, in the pads on the under side of the Dog’s 
foot), it seems obvious that they minister, not to sensation, 
but to the nutrition of that protective coating ($ 492). But — 
in other papille the blood-vessels are comparatively scanty, 
their interior being chiefly occupied by little cushions of con- 
densed areolar substance to which the sensory nerves proceed 
and as their Epidermic coating is thin, and as the degree 
of sensibility of any part of the skin bears a close correspond-— 
ence to the number of these papille which are included © 
within a given area of ifs surface, it can scarcely be doubted 
that they are the special instruments of the sense of Touch. 
491. The true skin, or Cutis (§ 37), from which alone "| 
leather is prepared, is thicker in most Mammals than in- 
Man ; but the thickness of the skin does not by any means ~ 
involve (as is commonly supposed) deficient sensibility. Thus, 
in the Spermaceti Whale it has been observed that the 
sensory nerves, which are destined to be distributed on the ] 
skin, pass through the blubber without giving off any con- | 
siderable branches, but spread out into a network of extreme} 
minuteness as soon as they arrive near the surface. It rl 
a fact well known to Whale-fishers, especially to those who — 
pursue this species, that these animals have the power of | 
