ON
FRACTURES, DISLOCATIONS, &c.
MEMOIR I.
ON THE FRACTURE OF THE CONDYLES OF THE LOWER JAW.
§ I.
1. The lower jaw, a kind of moveable hammer, destined, to use the words of a certain physiologist, to triturate the aliments against the almost immoveable anvil of the upper jaw, is more exposed to the action of external bodies, and consequently to fractures, than most of the other bones of the face. But all parts of it are not alike subject to such accidents. Common in its body, but less frequent in its branches or sides, fractures sometimes occur in the two processes in which its branches terminate. One of these processes, concealed by the zygoma, embosomed in the temporal muscle, and covered by the masseter, is less liable to fractures than the other, which serves as the centre of the motions performed by the bone, and is protected externally only by the parotid gland.
§ II.
2. A fracture of the condyle may sometimes arise from a counter-stroke, as when, in consequence of some external force being applied from before backwards, and from below upwards against the chin, this process is driven against the projecting rim of the glenoid cavity; at other times it may be the effect of an immediate or direct stroke, as when a body in motion strikes with force against the region of the joint, and does violence to that portion of the bone.