Dissection(6g. 130). The head being shaved, and a block placed beneath the back of the neck, make a vertical incision through the skin from before back wards, commencing at the root of the nose in front, and terminating behind at the occipital protuberance ; make a second incision in a horizontal direction along the forehead and around the side of the head, from the anterior to the posterior extremity of the preceding. Raise the skin in front from the subjacent muscle from below upwards; this must be done with extreme care, on account of their intimate union. The tendon of this muscle is best avoided by removing the integument from the outer surface of the vessels and nerves which lie between the two.

The superficial fascia in the epicranial region is a firm, dense layer, intimately adherent to the integument, and to the Occipito-frontalis and its tendinous aponeu-rosis; it is continuous, behind, with the superficial fascia at the back part of the neck; and, laterally, is continued over the temporal aponeurosis: it contains between its layers the small muscles of the auricle, and the superficial temporal vessels and nerves.

The Occipito-frontalis (fig. 131) is a broad musculo-fibrous layer, which covers over the whole of one side of the vertex of the skull, from the occiput to the eyebrow. It consists of two muscular bellies, separated by an intervening tendinous aponeurosis. The occipital portion, thin, quadrilateral in form, and about an inch and a half in length, arises from the outer two-thirds of the superior curved line of the occipital bone, and from the mastoid portion of the temporal. Its fibres of origin are tendinous, but they soon become muscular, and ascend in a parallel direction to terminate in the tendinous aponeurosis. The frontal portion is thin, of a quadrilateral form, and intimately adherent to the skin. It is broader, its fibres are longer, and their structure more pale than the occipital portion. Its internal fibres are continuous with those of the Pyramidalis nasi. Its middle fibres become blended with the Corrugator supercilii and Orbicularis: and the outer fibres are also blended with the latter muscle over the external angular process. The inner margins of the two frontal portions of the muscle are joined together for some distance above the root of the nose; but between the occipital portions there is a considerable but variable interval.

The aponeurosis covers over the whole of the vertex of the skull without any separation into two lateral parts, and is connected with the occipital and frontal portions of the muscle. Behind, it is attached, in the interval between the occipital origins, to the occipital protuberance and superior curved lines above the attachment of the trapezius; in front, it forms a short angular prolongation between the frontal portions; and on each side, it has connected with it the Attollens and Attrahens aurem muscles: in this situation it loses its aponeurotic character, and is continued over the temporal fascia to the zygoma by a layer of laminated areolar tissue. This aponeurosis is closely connected to the integument by a dense fibro-cellular tissue, which contains much granular fat, and in which ramify the numerous vessels and nerves of the integument; it is loosely connected with the pericranium by a quantity of loose cellular tissue, which allows of a considerable degree of movement of the integument.

Nerves. The Occipito-frontalis is supplied (frontal portion) by the supra-orbital and facial nerves; (occipital portion) by the posterior auricular branch of the facial and the small occipital.

Actions. This muscle raises the eyebrows and the skin over the root of the nose; at the same time it throws the integument of the forehead into transverse wrinkles, a predominant expression in the emotions of delight. It also moves the scalp from before backwards, by bringing alternately into action the occipital and frontal portions.