chap, vii.] THE LOWER JAW. 97 



downwards and backwards, so as to immediately 

 resist any movement of the condyle towards the 

 slender wall of bone that bounds the meatus and 

 tympanum. Were it not for this ligament, a blow 

 upon the chin would be a much more serious accident 

 than it is at present. It follows, from the proximity 

 of the joint to the middle ear, that disease in the 

 articulation may be set up by suppuration in this 

 part. In one case (Holmes' " System of Surgery "), 

 suppurative disease, spreading from the middle ear, 

 not only involved the joint, but induced necrosis of 

 the condyle of the lower jaw. The necrosed condyle 

 was removed entire from the auditory meatus, into 

 which cavity it had projected. 



Dislocation. This joint permits only of one 

 form of dislocation, a dislocation forwards. It may 

 be unilateral or bilateral, the latter being the more 

 usual, and it can only occur when the mouth happens 

 to be wide open. Indeed, the dislocation is nearly 

 always due to spasmodic muscular action when the 

 mouth is open, although in some few cases it has been 

 brought about by indirect violence, as by a downward 

 blow upon the lower front teeth, the mouth being 

 widely opened. It has occurred during yawning, 

 violent vomiting, etc. In more than one case the 

 accident happened while a dentist was taking a cast 

 of the mouth. Hamilton quotes a bilateral dislocation 

 in a woman during the violent gesticulations incident 

 to the pursuit of scolding her husband. When the 

 mouth is widely opened the condyles, together with 

 the interarticular nbro-cartilage, glide forwards. The 

 nbro-cartilage extends as far as the anterior edge of the 

 eminentia articularis, which is coated with cartilage 

 to receive it. The condyle never reaches quite so far as 

 the summit of that eminence. All parts of the capsule 

 save the anterior are rendered tense. The coronoid 

 process is much depressed. Now if the external 

 H 



