20 ON THE STRUCTURE AND 



as belonging chiefly to the extremities, which have Inrg 

 nerves, and a very vascular skin. In men, this is confined 

 to the extremities of the upper limbs; whilst the Apes 

 and Monkeys have it in all their feet. The lips of quadru- 

 peds have likewise this structure, as well as the snouts of 

 the Hog, the Hedgehog, Shrew, Mole, &c. and the pro- 

 boscis of Elephants, in all of which the sense of touch is 

 supposed to be greatly finer than that in the human hand. 



All the mammiferous animals are covered or enveloped 

 externally with a skin, consisting of an upper, thin, white, 

 and elastic layer, denominated epidermis or cuticle ; and, 

 beneath this, a much thicker layer, composed of numerous 

 fibres, closely interwoven, and disposed in various directions, 

 called the ctitis, or true skin. Through the pores of the 

 skin is continually, and insensibly, discharged an extremely 

 subtile fluid. These pores, in the human body, are so mi- 

 nute, that a grain of sand will cover more than a hundred 

 thousand of them ; and their daily discharge of fluid has 

 been calculated at upwards of three pounds weight. In 

 most of the quadrupeds the skin is hard to the touch, and 

 thickly clad with hair. Each of the hairs is placed in a 

 capsule or socket, and springs from a bulb at its lower ex- 

 tremity: There is, in this bulb, a vascular pyramid, upon 

 which the hair is formed, and by which it is generally 

 rendered tubular. The hair grows continually, but it usu- 

 ally falls off and is renewed once, and sometimes twice, in 

 the year. Concealed by the long hairs of most animals, 

 there is a short kind of down or wool, spread over the whole 

 body, and rising immediately out of the skin. 



With respect to the structure and appearance of the long 

 hair of different quadrupeds, we may remark, that each of 

 the hairs of the common Seal is waved : that those in the 

 tail of the Elephant are forked at the extremity. In some 

 animals, as the Squirrel, the Water Rat, and Meadow 



Mouse, 



