ii4 SURGICAL APPLIED ANATOMY. [Chap, vn 



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 

 fibre-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 

 pterygoid muscle (the muscle mainly answerable for 

 the luxation) contract vigorously, the condyle is soon 

 drawn over the eminence into the zygomatic fossa, the 



