THE MOUTH AND THROAT. 



117 



The pus may not only point in the mouth but can work its way laterally. In 

 such a case it may pass out behind the sheath of the great vessels and make its 

 appearance, as I have seen it, behind the posterior edge of the sternomastoid muscle. 

 If a tumor is present in this situation, the pus may be evacuated by an incision at 

 this point and the abscess drained there instead of making an opening through the 

 pharynx. This, of course, tends to guard against infection from the mouth. 



Lingual Nerve. The lingual nerve or gustatory branch of the fifth can be 

 readily exposed in the mouth. On looking into the mouth, a fold can be seen going 

 up and back just behind the last molar tooth. This is formed by the pterygomandib- 

 ular ligament, running from the tip of the internal pterygoid plate to the posterior 

 extremity of the mylohyoid ridge and joining the buccinator with the superior con- 



Mandibular (inferior 

 dental) nerve 



Mandibular (inferior 

 dental) artery 



Mandibular spine 

 (Spix) 



Lingual nerve 

 Submaxillary gland 



laxillary duct 

 al gland 



FIG. 146. View of mandibular and lingual nerves from within. 



stricter muscles. An incision made just internal to this fold, below and behind the 

 last molar tooth, will lead one down to the lingual nerve close to the bone. 



The mandibular nerve is also reached through an incision running from the 

 last upper to the last lower molar tooth. The finger is introduced and the spine of 

 Spix felt at the inferior dental foramen. The nerve and artery enter the mandible at 

 this point, the artery being below and posterior. The operation of Paravicini on this 

 nerve through the mouth is unsatisfactory on account of the lack of proper exposure. 

 It is better to attack the nerve from the outside as detailed on page 60. 



PHARYNX. 



The pharynx is the common air and food tract that lies behind the nose, mouth, 

 and larynx. It extends from the base of the skull above to the oesophagus below. 

 Its lower end is at the cricoid cartilage, which is opposite the sixth cervical vertebra. 

 In passing an instrument directly backward through the nose, one strikes the base of 

 the skull or interval between the basilar process and the atlas. In looking into the 

 throat through the mouth, one is level with the body of the second vertebra. If, by 

 means of a hook, the soft palate is raised or pushed aside and the head tilted slightly 

 backward one sees the anterior tubercle of the atlas. The rounded projection can 



