THE FACE, MOUTH AND PHARYNX 183 



branch of the trigeminal, and leaves the skull through the 

 foramen ovale. It at once breaks up into numerous branches, 

 which at first lie deep to the external pterygoid and on 

 the lateral wall of the nasal pharynx. 



The nerve may be reached, for the purposes of injection, by 

 inserting a needle immediately below the zygomatic arch at a 

 point 2-5 cm. in front of the external acoustic meatus. It is 

 directed medially and slightly backwards to a depth of 4 cm., 

 when the point comes into contact with the nerve (Symington). 

 Before reaching the nerve, the needle pierces the masseter 

 muscle and passes through the mandibular (sigmoid) notch, 

 the temporal and external pterygoid muscles. If the needle 

 is passed in for more than 4 cm. it pierces the lateral wall of the 

 nasal pharynx. 



Branches. (i) The Auricula-temporal nerve passes back- 

 wards into the parotid gland (pp. 174, 211). (2) The Buccinator 

 (long buccal) pierces the external pterygoid, and frequently the 

 anterior fibres of the temporal, before it appears in the face (p. 

 174). (3) The Inferior Alveolar (Dental) nerve runs downwards, 

 deep to the external but superficial to the internal pterygoid, 

 and enters the mandibular foramen in company with the artery 

 of the same name. As it enters the foramen it gives off (4) the 

 Mylo-hyoid nerve (p. 144). (5) The Lingual nerve lies just anterior 

 to the inferior alveolar. On the inner surface of the body of 

 the mandible it lies above the mylo-hyoid line and, opposite the 

 third molar (p. 184) tooth it is only covered by the mucous 

 membrane of the mouth. (6) The remaining branches of the 

 mandibular nerve are all motor and supply the muscles of 

 mastication, viz. the temporal, the masseter, and the external 

 and internal pterygoids. Paralysis of this nerve is referred to 

 on p. 181. 



The inferior alveolar and lingual nerves are sometimes 

 involved in severe neuralgia, which affects the lower teeth and 

 gums and the tongue. They may be approached (i) through 

 the skin of the cheek, or (2) from the inside of the mouth. 



i. A curved incision is carried down the lower part of the 

 posterior border of the ramus and forwards along the inferior 

 border of the mandible. This incision passes down to the bone 

 at once, and a flap, consisting of all the superficial structures, 

 including the periosteum, is thrown forwards. The ramus is 

 then trephined slightly above the last molar tooth, and the 

 piece of bone is removed, exposing the periosteum on its deep 



