The external covering of the body, whether of the vegetable or of the animal organism, is familiarly known as the skin, a word of somewhat obscure derivation, most probably going back to the Anglo-Saxon. Integument, however, derived from tego, to cover, at once conveys the proper meaning. No one word, however, can express the character of the structures of which the integument is composed, nor the important functions which it is designed to perform.

In its physiological signification the skin takes its place among the organs of special sense, being largely supplied with nerves which are capable of appreciating the impressions resulting from contact with other bodies, and also impressions of weight and alterations of temperature. In describing its structure it is usual to refer to two principal layers, the outer, composed of cells, and called the cuticle or epidermis, and the lower, entitled the derma or chorium or cutis.