98 



THE SKELETON. 



divide the body of the bone into a superior or alveolar and an inferior or basilar 

 portion. 



The superior or alveolar border is wider, and its margins thicker, behind than 

 in front. It is hollowed into numerous cavities, for the reception of the teeth ; 

 these cavities are sixteen in number, and vary in depth and size according to the 

 teeth which they contain. To its outer side, the Buccinator muscle is attached as 

 far forward as the first molar tooth. The inferior border is rounded, longer than 

 the superior, and thicker in front than behind ; it presents a shallow groove, just 

 where the body joins the ramus, over which the facial artery turns. 



OENIO-HYO-OLOSSUS. 



GENrO-HYOIDEUS. 



Mylo-liyoid ridge. 



Body. 



FIG. 66. Inferior maxillary bone. Inner surface. Side view. 



The Perpendicular Portions, or Kami, are of a quadrilateral form. Each 

 presents for examination two surfaces, four borders, and two processes. The 

 external surface is flat, marked with ridges, and gives attachment throughout nearly 

 the whole of its extent to the Masseter muscle. The internal surface presents 

 about its centre the oblique aperture of the inferior dental canal, for the passage 

 of the inferior dental vessels and nerve. The margin of this opening is irregular ; 

 it presents in front a prominent ridge, surmounted by a sharp spine, the lingula, 

 which gives attachment to the internal lateral ligament of the lower jaw, and at 

 its lower and back part a notch leading to a groove, the mylo-hyoidean, which runs 

 obliquely downward to the back part of the submaxillary fossa, and lodges the 

 mylo-hyoid vessels and nerve. Behind the groove is a rough surface, for the 

 insertion of the Internal pterygoid muscle. The inferior dental canal rims obliquely 

 downward and forward in the substance of the ramus, and then horizontally 

 forward in the body ; it is here placed under the alveoli, with which it communi- 

 cates by small openings. On arriving at the incisor teeth, it turns back to 

 communicate with the mental foramen, giving off two small canals, which run 

 forward, to be lost in the cancellous tissue of the bone beneath the incisor teeth. 

 This canal, in the posterior two-thirds of the bone, is situated nearer the internal 

 surface of the jaw ; and in the anterior third, nearer its external surface. Its 

 walls are composed of compact tissue at either extremity, and of cancellous in the 

 centre. It contains the inferior dental vessels and nerve, from which branches are 

 distributed to the teeth through small apertures at the bases of the alveoli. The 

 lower border of the ramus is thick, straight, and continuous with the body of the 

 bone. At its junction with the posterior border is the angle of the jaw, which is 

 either inverted or everted, and marked by rough, oblique ridges on each side, for 



