The skin of the sheep, in common with that of most animals, is composed
of three textures. Externally is the cuticle, or scarf-skin, which is
thin, tough, devoid of feeling, and pierced by innumerable minute holes,
through which pass the fibres of the wool and the insensible
perspiration. It seems to be of a scaly texture; although is not so
evident as in many other animals, on account of a peculiar
substance--the yolk--which is placed on it, to protect and nourish the
roots of the wool. It is, however, sufficiently evident in the scab and
other cutaneous eruptions to which this animal is liable.
Below this cuticle is the _rete mucosum_, a soft structure; its fibres
having scarcely more consistence than mucilage, and being with great
difficulty separated from the skin beneath. This appears to be placed as
a defence to the terminations of the blood-vessels and nerves of the
skin, which latter are, in a manner, enveloped and covered by it. The
color of the skin, and probably that of the hair or wool also, is
determined by the _rete mucosum_; or, at least, the hair and wool are of
the same color as this substance.
Beneath the _rete mucosum_ is the _cutis_, or true skin, composed of
numberless minute fibres crossing each other in every direction; highly
elastic, in order to fit closely to the parts beneath, and to yield to
the various motions of the body; and dense and firm in its structure,
that it may resist external injury. Blood-vessels and nerves innumerable
pierce it, and appear on its surface in the form of _papillae_, or
minute eminences; while, through thousands of little orifices, the
exhalent absorbents pour out the superfluous or redundant fluid. The
true skin is composed, principally or almost entirely, of gelatine; so
that, although it may be dissolved by long-continued boiling, it is
insoluble in water at the common temperature. This organization seems to
have been given to it, not only for the sake of its preservation while
on the living animal, but that it may afterwards become useful to man.
The substance of the hide readily combining with the tanning principle,
is converted into leather.