182 THE HEAD AND NECK 



up the posterior border of the ramus. The incision, which 

 must not be carried upwards too far lest the facial nerve be 

 injured (p. 178), penetrates down to the bone, and the periosteum 

 may be stripped off along with the masseter laterally and the 

 internal pterygoid medially, so as to leave the tuberculous bone 

 exposed. The affected area may then be removed without 

 opening into the mouth. 



In Excision of the Mandible for malignant disease the bone is 

 removed along with its periosteal covering. The incision begins 

 at the margin of the lower lip and is carried down in the middle 

 line to the lower border of the bone, along which it is carried 

 backwards to the angle. In this part of the incision, the external 

 maxillary artery and its accompanying vein are cut through 

 and secured. The incision is then carried upwards along the 

 posterior border of the ramus to the level of the tragus. It is 

 only skin-deep above, so that the facial nerve is not injured. 

 The soft parts are reflected from the lateral aspect of the bone 

 and the masseter is cut away from its insertion, and the mucous 

 membrane is divided as it is reflected from the cheek on to the 

 external aspect of the gum. A Gigli saw is passed upwards, 

 internal to the bone, through an opening made in the mylo- 

 hyoid a little to one side of the median plane, and it is brought 

 out into the mouth through the mucous membrane of its floor. 

 The mandible is then divided through the socket of the lateral 

 incisor tooth, and in this way the mental spine (genial elevation), 

 with its muscular attachments, is left intact. The bone is 

 next depressed and dragged outwards through the wound, and 

 the origin of the mylo-hyoid and the mucous membrane on the 

 inner aspect of the gum are cut through, until the internal ptery- 

 goid is reached. When the muscle and the spheno-mandibular 

 (internal lateral) ligament, which lies on its surface, have been 

 divided, the inferior alveolar artery and nerve are exposed 

 between them and the ramus. After they have been secured, 

 the bone may be depressed still further so as to bring the coronoid 

 process into view. It may be cut across, 01 the temporal muscle 

 may be detached from its insertion. The mandible is now only 

 held in position by the external pterygoid and the temporo- 

 mandibular joint. 



If these structures are cut through with the knife, the internal 

 maxillary artery (p. 181) is in great danger, and it is safer to 

 twist the condyle away from its attachments. 



The Mandibular (Inferior Maxillary) Nerve is a 



