THE FACE, MOUTH AND PHARYNX 181 



auriculo-temporal nerves. If the nerve is completely paralysed, 

 the area supplied by its mental branch loses its sensibility, 

 and when drinking, the patient can only appreciate the glass 

 with his lips on the uninjured side. 



The Temporal Muscle arises from the temporal fossa and descends under 

 cover of the zygomatic arch, to be inserted into the margins and deep surface 

 of the coronoid process. The Masseter arises from the zygomatic arch, and 

 is inserted into the lateral surface of the mandibular ramus. Both muscles 

 are powerful elevators of the mandible, and are supplied by the mandibular 

 division of the trigeminal nerve. 



The External Pterygoid arises from the skull in the region of the pterygoid 

 process (plates) of the sphenoid, and passes almost horizontally backwards, 

 to be inserted into the condyle and the articular disc (p. 180). Its action is 

 to draw the condyle and the articular disc forwards, thus protruding the 

 mandible. As it passes backwards it is in contact with the deep surface of 

 the temporal muscle. The Internal Plerygoid has a similar but deeper origin. 

 Its fibres run downwards and laterally, as well as backwards, to reach the 

 internal surface of the angle of the mandible. Both pterygoid muscles are 

 supplied by the mandibular division of the trigeminal. When the two ptery- 

 goid muscles of one side act alone, the mandible is twisted over to the opposite 

 side. This action is seen in lateral chewing movements, and in paralysis of 

 the mandibular nerve the mandible is permanently pulled over to the same 

 side as the lesion. 



The Internal Maxillary Artery arises from the external 

 carotid in the parotid gland at the level of the neck of the 

 mandible. It passes forwards deep to the bone but superficial 

 to the spheno-mandibular ligament. It may run either super- 

 ficial or deep to the external pterygoid, and it terminates in the 

 pterygo-palatine (spheno-maxillary) fossa, where it gives off 

 the palatine, infra-orbital, and numerous other small branches. 

 In the earlier part of its course the artery gives off (i) the middle 

 meningeal, which ascends deep to the external pterygoid, to 

 enter the skull through the foramen spinosum ; (2) the inferior 

 alveolar (dental), which enters the mandibular foramen ; and (3) 

 branches to the surrounding muscles. The corresponding veins 

 form a plexus round the pterygoid muscles, which communicates 

 with the cavernous sinus (p. 225) above, the anterior facial 

 vein in front, and the posterior facial vein (temporo-maxillary) 

 behind. 



Operations on the Mandible. The periosteum of the 

 mandible is thick and strong, and can be easily stripped off the 

 bone. Further, it is able to reform large portions of the bone 

 after subperiosteal resection, an operation which is employed 

 with advantage in tuberculous and chronic septic disease of the 

 body and ramus. A curved incision is made along the posterior 

 third of the inferior border of the body, round the angle, and 



