Muscles of the Skin

There appear to be two kinds of muscles found in the skin - the voluntary, or striated, and the involuntary. The former are to be detected in the face, beard, and nose, "ascending sometimes obliquely, sometimes vertically, between the hairs and the sebaceous follicles to terminate in the corium" (Biesiadecki). They come from below. The organic or non-striated muscles are more abundant. They occur forming a kind of network in the scrotum. Over the general surface of the skin bands of fibres are detected in connection with the hair follicle, and are called arrectores pili. There muscles exist as single fasciculi .045 to .22 of a millimetre, sometimes on one, sometimes on both sides of the hair follicle, in immediate relation to the sebaceous glands, which they enclose more or less. They run from the corium above to the part of the hair follicle just below the glands, and there end in the inner sheath of the hair follicle. Some authors affirm that bundles go down to the subcutaneous tissue and send off vertical and horizontal branches. Neuman, who is of this opinion, states that bands run above and under the sweat glands, more especially in the axilla. He describes also independent bundles of muscle in the corium quite unconnected with the hair follicles.