172 THE SKELETON. 



longer than the superior, and thicker in front than behind; it presents a 

 shallow groove, just where the body joins the ram us, over which the facial 

 artery turns. 



The Perpendicular Portions, or Rami, 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 open- 

 ing 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 submaxil- 

 lary 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 runs obliquely downwards and forwards in the sub- 

 stance of the ramus, and then horizontally 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 forward, to be lost in the can- 

 cellous 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 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 poste- 

 rior the condyloid. 



The coronoid process is a th*in, flattened, triangular eminence of bone, which 

 varies in shape and size in different subjects, and serves chiefly 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 lon- 

 gitudinal 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 the alveolar process ; this ridge and part of the groove afford attach- 

 ment, above, to the Temporal; below, to the Buccinator muscle. 



The condyloid process, shorter but thicker than the coronoid, consists of two 

 portions : the condyle, and the constricted portion which supports the condyle, 

 the neck. The condyle is of an oblong form, its long axis being transverse, 

 and set obliquely on the neck in such a manner that its outer end is a little 

 more forward and a little higher than its inner. It is convex from before back- 

 wards, and from side to side, the articular surface extending further on the 

 posterior than on the anterior surface. The neck of the condyle is flattened 

 from before backwards, and strengthened by ridges which descend from the 

 fore part and sides of the condyle. Its lateral margins are narrow, and present 

 externally a tubercle for the external lateral ligament. Its posterior surface is 

 convex ; its anterior is hollowed out on its inner side by a depression (the 

 pterygoid fossa) for the attachment of the External Pterygoid. 



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 the attachment of the Masseter externally, and the Internal 

 Pterygoid internally ; the stylo-maxillary ligament is attached to the bone be- 

 tween these muscles. The anterior border is thin above, thicker below, and 

 continuous with the external oblique line. The posterior border is thick, smooth, 

 rounded and covered by the parotid gland. 



