Masseter.
Temporal.

The Masseter muscle has been already exposed by the removal of the integument from the side of the face (fig. 131).

The Masseter is a short thick muscle, somewhat quadrilateral in form, consisting of two portions, superficial and deep. The superficial portion, the largest part of the muscle, arises by a thick tendinous aponeurosis from the malar process of the superior maxilla, and from the anterior two-thirds of the lower border of the zy-gomatic arch: its fibres pass downwards and backwards, to be inserted into the lower half of the ramus and angle of the lower jaw. The deep portion is much smaller, more muscular in texture, and the direction of its fibres is forwards; it arises from the posterior third of the lower border and whole of the inner surface of the zygomatic arch and is inserted into the upper half of the ramus and coro-noid process of the jaw. The deep portion of the muscle is partly concealed, in front, by the superficial portion; behind, it is covered by the parotid gland. The fibres of the two portions are united at their insertion.

Relations. By its superficial surface, with the integument; above, with the Orbicularis palpebrarum and Zygomaticus major; and has passing across it transversely, Stenon's duct, the branches of the facial nerve, and the transverse facial artery. By its deep surface, with the ramus of the jaw, the Temporal muscle, and the Buccinator, from which it is separated by a mass of fat. Its posterior margin is covered by the parotid gland. Its anterior margin is in relation, below, with the facial artery.

Dissection. In order to expose the Temporal muscle, this fascia should be removed : this may be effected by separating it at its attachment along the upper border of the zygoma, and dissecting it upwards from the surface of the inuacle. The zygomatic arch should

At this stage of the dissection, the temporal fascia is seen covering in the Temporal muscle. It is a strong aponeurotic investment, affording attachment, by its inner surface, to the superficial fibres of this muscle. Above, it is a single uniform layer, attached to the entire extent of the temporal ridge; but below, where it is attached to the zygoma, it consists of two layers, one of which is inserted into the outer, and the other to the inner border of the zygomatic arch. A small quantity of fat, and the orbital branch of the temporal artery, are contained between these. It is covered, on its outer surface, by the aponeurosis of the Occipito frontalis, the Orbicularis palpebrarum, and Attollens and Attrahens aurem muscles; the temporal artery and vein, and ascending branches of the temporal nerves, cross it from below upwards. Then be divided in front at its junction with the malar bone, and, behind, near the external auditory meatus, and drawn downwards with the masseter, which should be detached from its insertion into the ramus and angle of the jaw. The whole extent of the Temporal muscle is then exposed.

The Temporal is a broad radiating muscle, situated at the side of the head, and occupying the entire extent of the temporal fossa. It arises from the whole of the temporal fossa, which extends from the external angular process of the frontal in front, to the mastoid portion of the temporal behind, and from the curved line on the frontal and parietal bones above, to the pterygoid ridge on the great wing of the sphenoid below. It is also attached to the inner surface of the temporal fascia. Its fibres converge as they descend, the anterior passing obliquely backwards, the posterior obliquely forwards, and the middle fibres descend vertically, and terminate in an aponeurosis, the fibres of which, radiated at its commencement, converge into a thick and flat tendon, which is inserted into the inner surface, apex, and anterior border of the coronoid process of the lower jaw.

Relations. By its superficial surface, with the integument, the temporal fascia, aponeurosia of the Occipito-frontalis, the Attollens and Attrahens aurem muscles, the temporal vessels and nerves, the zygoma and Masseter. By its deep surface, with the temporal fossa, the External pterygoid and part of the Buccinator muscles, the internal maxillary artery, and its deep temporal branches.

Nerves. Both muscles are supplied by the inferior maxillary nerve.