94 



OSTEOLOGY. 



a shallow groove, just where the body joins the ramus, over which the facial 

 artery turns. 



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 pre- 

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

 passage of the inferior dental vessels and nerve. The margin o'f this opening 

 is irregular ; it presents in front a prominent ridge, surmounted by a sharp spine, 

 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 downwards 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 descends 

 obliquely downwards and forwards in the substance of the ramus, and then hori- 

 zontally forwards in the body ; it is here placed under the alveoli, with which it 

 communicates 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 



Fig. 57. Inferior Maxillary Bone. Inner Surface. Side View. 



CENIO-HYO-GLOSSUS 

 CENIO-HYOIDEU5 



Mi/la- hi/ai 



Bod 



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, runs nearest the internal sur- 

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

 are composed of compact tissue at either extremity, 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 upper border 

 of the ramus is thin, and presents two processes, separated by a deep concavity, 

 the sigmoid notch. Of these processes, the anterior is the coronoid, the posterior 

 the condyloid. 



The Coronoid Process is a thin, flattened, triangular eminence of bone, which 

 varies in shape and size in different subjects, and serves essentially for the attach- 

 ment of the Temporal muscle. Its external surface is smooth, and affords 

 attachment to the Masseter and Temporal muscles. Its internal surface gives 

 attachment to the Temporal muscle, and presents the commencement of a longi- 

 tudinal ridge, which is continued to the posterior part of the alveolar process. On 

 the outer side of this ridge is a deep groove, continued below on the outer side of 



