OCR Text |
Show 354 MR. P. CHALMERS MITCHELL ON THE [May 7, most external portion is the largest. It arises fleshy from a curved line over the ear from the posterior edge of the orbit to the edge of the biventer maxillae. Its fibres run downwards and forwards under the maxilla, to be inserted along the inner edge of the mandible. Tbe second portion is the most anterior. It is a com-tively narrow band, strongly tendinous, passing from the posterior inner wall of the orbit near the postorbital process : its fibres run downwards and outwards, and, passing under the maxilla, are inserted into the mandible internal to the first portion. The third portion lies behind the second, and is shorter. It arises from the tinder edge of the orbital process of the quadrate, and, passing parallel to the second portion under the maxillary bar, is inserted into the inner side of the mandible. The fourth portion does not act as an elevator of the lower jaw. It is a broad fleshy mass, deep within the orbit, passing from behind the optic foramen to the upper and inner edge of the orbital process of the quadrate. Pterygoid. The first portion is muscular only at its origin from the internal articular process of the lower jaw. It becomes a strong superficial band of tendon, which in front spreads out in the strong membrane covering the palate. The second portion is a broad muscular mass arising from the internal articular process all along its length. The fibres run forwards and are inserted to the pterygoid and the ventral surface of the palatal bones. The third portion is a broad mass external to the second; it arises from the inner face of the lower jaw behind the second portion, and running forwards and inwards is inserted to the outer and upper surfaces of the palatal bone. The Hyoid Group. Mylohyoid anterior. The two divisions seen in Palamedea were not marked: the muscle, which was well marked, arises from the inner side of the lower jaw anterior to the region of the basihyal. The fibres run straight across the surface of the lower jaw and meet their fellows of the other side in a median raphe. Some of the posterior fibres spread out as a diffuse sheet. Mylohoid posterior. The origin was as in Palamedea. The posterior thinner portion was exactly as in Palamedea, where we described it as a platysma myoides. The narrower anterior portion was a stout ribbon of muscle running forwards and inwards superficial to the ceratohyal, to be inserted to the inner surface of the base of the cornu and to the outer surface of the urohyal, in fact to the angle formed by the meeting of these two parts of the hyoid apparatus. Geniohyoid. As in Palamedea this muscle was wrapped round the posterior portion of the cornu of the hyoid, and then passed forward to be inserted to the inner surface of the lower jaw behind the anterior mylohyoid. Genioglossus absent, as in Palamedea, |