THE MANDIBLE 



175 



bone and undergo absorption. The inner alveolar border, usually described as arising from a 

 separate ossific center (splenial center), is formed in the human mandible by an ingrowth from 

 the main mass of the bone. At birth the bone consists of two parts, united by a fibrous symphysis, 

 in which ossification takes place during the first year. 



The foregoing description of the ossification of the mandible is based on the researches of 

 Low 1 and Fawcett, 2 and differs somewhat from that usually given. 



Articulations. The mandible articulates with the two temporal bones. 



Mental nerve 



Mylohyoid nerve 



Fio. 178. Mandible of human embryo 24 mm. 

 long. Outer aspect. (From model by Low.) 



Lingual nerve 

 Inf. alveolar n. 



Mylohyoid nerve 

 Chorda tympani 



Stapes 

 Facial nervf 



Reicherfs cartilage 



FIG. 179. Mandible of human embryo 24" mm. long. 

 Inner aspect. (From model by Low.) 



Mandibular nerve 

 Meckel's cartilage 



Mental nerve 



Anterior process of malleus 



Fio. 180. Mandible of human embryo 95 mm. long. Outer aspect. Nuclei of cartilage stippled. 



(From model by Low.) 



Auriculotemporal nerve 



Lingual nerve 



Ant. process of malleus 

 Chorda tympani 



Sympnysis 



Mylohyoid nerve 



Fio. 181. Mandible of human embryo 95 mm. long. Inner aspect. Nuclei of cartilage stippled. 



(From model by Low.) 



CHANGES PRODUCED IN THE MANDIBLE BY AGE. 



At birth (Fig. 182) the body of the bone is a mere shell, containing the sockets of the two 

 incisor, the canine, and the two deciduous molar teeth, imperfectly partitioned off from one 

 another. The mandibular canal is of large size, and runs near the lower border of the bone; the 

 mental foramen opens beneath the socket of the first deciduous molar tooth. The angle is obtuse 

 (175), and the condyloid portion is nearly in line with the body. The coronoid process is of 

 comparatively large size, and projects above the level of the condyle. 



1 Proceedings of the Anatomical and Anthropological Society of the University of Aberdeen, 1905, and Journal of 

 Anatomy and Physiology, vol. xliv. 



2 Journal of the American Medical Association, September 2, 1905. 



