BONES OP THE FACE. 209 



six bones, i. e. the sphenoid, ethmoid, two upper maxillary, 

 and two palate. 



Inferior Maxillary Bone (os maxillare inferius^The 

 inferior maxilla, or lower 

 jaw, is situated at the lower 

 part of the face, occupying the 

 front and sides, and extending 

 as far back as the base of the 1 

 skull. Its form is semi-circu- 

 lar, and consists of a body and 

 two extremities. The body 

 forms the central and lateral 

 portions. The central portion 

 is prominent, known as the chin, and has a vertical ridge 

 along its median line, the sympliysis menti, which denotes the 

 original separation -of this bone into two symmetrical parts. 



The anterior surface of the chin often presents a trian- 

 gular shape, the base below having, at either end, a promi- 

 nent process, while the apex is above. On either side of 

 the symphysis is a depression for the origin of the depres- 

 sor labii inferioris muscle; and external to this is an ob- 

 lique opening, the anterior mental foramen, through which 

 come out the inferior dental nerve and artery. On the 

 posterior part of the chin the surface is concave, except in 

 the middle line of the symphysis, where is seen a chain of 

 eminences. To the upper one of these is attached the fre- 

 num linguce, to the middle, the genio-hyoglossi, and to the 

 lower, the genio-Jiyoidei muscles. On either side of this 

 middle line, and at the upper part, are two depressions for 

 the sublingual glands, and, at the lower part likewise, de- 

 pressions for the digastric muscles. The lateral portions 

 take a direction outwards and backwards; on their exter- 



FIG. 51 represents the inferior Maxillary Bone, a Body ; 6 Ramus ; c Sym- 

 physis menti ; d Alveolar process ; e Anterior mental foramen ; / Base ; g 

 Groove for the facial artery ; h Angle ; i Posterior portion of ridge for the 

 mylo-hyoid muscle ; j Coronoid process ; k Condyle ; / Neck of Condyloid pro- 

 cess; m Posterior mental foramen ; n. Groove for inferior maxillary nerve ; 

 o Molar teeth ; p Bicuspid teeth; q r Middle and lateral incisors. 



14 



