THE FACE 393 



vessels and nerves supplying the lower jaw and the teeth. This 

 canal occupies nearly all the interior of the body of the bone. In it, 

 from above, depend the hollow pegs which form the tooth-sockets ; 

 they are connected with the lateral walls by bands of cancellous 

 tissue. Inasmuch as these sockets are shorter in front, the canal 

 appears to be highest at the anterior premolar region. Each socket 

 is perforated to allow entrance and exit to the nerves and vessels of 

 the tooth. Behind the molar tooth the canal communicates with the 

 cancellous tissue ; it ends' in front at the side of the canine. The 

 anterior margin of the dental foramen is sharp, and on the upper 

 margin is frequently found a spine indicating the attachment of the 

 spheno-maxillary ligament. The external surface forms, behind, an 

 internal root for the condyloid process, below which it passes outward 

 and backward into the subcondyloid space. 



Nomenclature. Mandible is from mandibula, introduced by 

 Macrobius in the fifth century for both upper and lower jaws. It 

 is derived from mandere, to chew. Pliny (A.D. 23-79) employed 

 maxilla inferior, whence the name the inferior maxillary bone. The 

 Germans have das Unterkieferbein and der Kinnlade. The French 

 have le maxillaire inferieur. 



Articulation. The mandible articulates with the temporal bone 

 of the cranium. 



Muscular Attachments. To the outer surface of the lower jaw 

 are attached the temporal, the masseter, and the buccinator ; to the 

 inner surface, the external pterygoid, the internal pterygoid, the 

 maxillo-auricular, the mylo-hyoid, the genio-hyoid, and the genio- 

 hyo-glossus ; to both surfaces and the lower border, the digastric. 



Ossification. Each half of the mandible develops from several 

 centres of ossification, which early unite. 



VARIATIONS IN THE MANDIBLE. 

 VARIATIONS IN SIZE. 



One-half of the mandible is measured as follows : 



The maximum length is the distance from the tip of the symphysis 

 to the posterior point of the condyle. 



The height of the ascending ramus is the vertical distance from 

 the top of the coronoid to the lower border of the bone. 



The length of the condyle is from the inner to the outer end. 



