ARTICULATION OF THE LOWER JAW. 213 



tition, it is nearly on a line with the mylo-hyoid ridge-; 

 and in old age, when the teeth are lost, it runs along the 

 alveolar "border. Its size also varies. Before the appear- 

 ance of the second teeth, and in the foetus, it is observed to 

 be very large ; it diminishes in the adult, and contracts 

 still more in old age. 



The development of the inferior maxilla is by two points 

 of ossification, one for each lateral half; their common 

 point of union being the symphysis. It and the clavicle 

 are the first bones formed. The lower edge of this bone is 

 seen to commence ossifying about the end of the first month, 

 and about the end of the second, each half of the bone pre- 

 sents a groove common to the dental canal and alveoli. 

 Union of the symphysis occurs during the first year. 



ARTICULATION OF THE LOWER JAW. 



It articulates with the temporal bones at the glenoid fos- 

 sae, and with the sixteen lower teeth. The condyles of the 

 inferior maxilla and that portion of the glenoid cavity of the 



A FIG. 52. B 



temporal bone, in front of the glasserian fissure, constitute 

 the bony portions which enter into the movable articulation 



FIG. 52, A represents an external view of the Articulation of the Lower Jaw. 

 a Zygomatic arch. 6 Tubercle of the zygoma, c Ramus of the lower jaw. 

 d Mastoid process of the temporal bone, e External lateral ligament. / Stylo- 

 maxillary ligament. 



FIG. 52, B represents an inner view of the same articulation, a Section 

 through the petrous portion of the temporal bone and spinous process of the 

 sphenoid, b Internal view of part of the body and ramus of the lower jaw. 

 c Interfial portion of the capsular ligament, d Internal lateral ligament. 

 e Point for passage of the mylo-hyoid nerve. / Stylo-maxillary ligament. 



