Temporo-Maxillary Joint 2 1 



symphysis, and when this is done the tongue must be brought out by 

 a strong loop, lest it fall back against the glottis. As the surgeon pro- 

 ceeds to denude the angle and ramus, he keeps his knife or raspatory 

 close to the bone, lest he injure the internal maxillary artery ; its 

 inferior dental branch, with the vein and nerve, must be cut just as 

 they enter the substance of the bone. The mucous membrane and 

 the floor of the mouth (mylo-hyoid) and the sub-maxillary and sub- 

 lingual glands are detached early in the operation, and the ramus is 

 at last held merely by the ligaments of the joint and the insertions of 

 the temporal and external pterygoid ; these are easily severed, the 

 coronoid process being perhaps snipped off with much of the temporal 

 insertion. 



Necrosis of more or less of the bone is generally the result of acute 

 inflammation, which may be caused by a bad tooth, or may occur in 

 the weakness left after measles or scarlet fever. The necrosis is due 

 to the fact that the lower jaw abounds in compact tissue, inflammatory 

 effusion quickly choking the vessels in the H aversian canals. 



The temporo-maxillary joint belongs in man to the division 

 arthrodia ; in some animals, as the badger, it is a perfect hinge. 

 Entering into its formation are that part of the glenoid cavity which 

 is in front of the Glaserian fissure, the eminentia articularis, and 

 the condyle. Each surface is covered with articular cartilage, but 

 interposed between the upper and lower planes of the joint is a 

 sinuous layer of inter-articular fibro-cartilage, which, receiving some 

 of the insertion of the external pterygoid, closely follows all the 

 movements of the condyle. The external lateral and the capsular 

 ligaments are also attached to the fibre-cartilage. The external 

 lateral ligament, a strong and short band, descends from the tubercle 

 at the root of the zygoma to the neck of the condyle, being attached 

 also to the inter-articular fibro-cartilage, as just noted. The internal 

 lateral ligament is a long and unimportant band between the spine of 

 the sphenoid and the inner edge of the inferior dental foramen. The 

 internal maxillary artery and the inferior dental vessels and nerve 

 pass between it and the jaw. As Tillaux remarks, the external lateral 

 ligament of one side is the internal lateral ligament for the other. 

 The stylo-maxillary ligament is but a piece of the deep cervical fascia ; 

 it separates the parotid and sub- maxillary glands. The capsular 

 ligament, a loose and unimportant sac, is attached around the glenoid 

 cavity and the neck of the condyle. 



There are two synovial membranes, one between the temporal bone 

 and the fibro-cartilage, and the other between it and the condyle. 

 They may communicate by a gap in the middle of the cartilage. 



Supply. The arteries are branches of the masseteric, and of the 

 vessels in the neighbouring parotid gland. The nerves come from the 

 masseteric and the auriculo-temporal of the third division of the fifth. 



Movements. The jaw is depressed by the platysma, mylo-hyoid, 



