156 



OSTEOLOGY. 



correspondence with the back of the lower part of the symphysis, there is a 

 raised tubercle surmounted by two laterally placed spines, the mental spines. 

 Occasionally these are again subdivided into an 

 upper and lower pair, or it may be that the lower 

 pair may fuse to form a rough median ridge. To 

 the upper pair of spines the genio-glossi muscles 

 are attached, whilst the lower pair serve for the 

 origin of the genio-hyoid muscles. Immediately 

 above the tubercle there is a median foramen for 

 the transmission of a nutrient vessel, and close 

 to the alveolar border opposite the intervals be- 

 tween the central and lateral incisors, there are 

 two little vascular canals. 



The ramus mandibulse passes upwards from 

 the posterior part s 



of the body, form- 

 ing by the junc- 

 tion of its pos- 

 terior border with 

 the base of the 

 booly the angulus 

 mandibulae (angle), 

 which is usually 

 rounded and more 



everted, i ^^~^^T < H^^^r^ 10 



FIG. 165. THE MEDIAL SIDE OF THE RIGHT HALF OF THE MANDIBLE. 

 5. Coronoid process. 



or 



The lateral sur- 

 face of the ramus 

 affords attach- 

 ment to the mas- 



10. Fossa for submaxillary 



gland. 



11. Mylo-hyoid line. 



12. Digastric fossa. 



Mental spines. 



Seter muscle, and 2. Surface in relation to 6. Condyloid process. 



When that muscle the sublin g ual g land - 7. Mandibular foramen. 



, ,-, T 3. Alveolar border. 8. Mylo-hyoid groove. 



is powerfully de- 4 . Lingula . 9 . Ang i e . 



veloped the bone 



is usually marked by a series of oblique curved ridges, best seen towards the 

 angle. About the "middle of the deep or medial surface is the large opening 

 (foramen mandibulare) of the inferior alveolar canal, which runs downwards 

 and forwards to reach the body, and transmits the inferior alveolar vessels 

 and nerve. This aperture is overhung in front by a pointed scale of bone, the 

 lingula mandibulae, to the edges of which the spheno-mandibular ligament 

 is attached. Behind the lingula and leading downwards and forwards for 

 an inch or so from the opening of the inferior alveolar canal is the sulcus 

 mylohyoideus (mylo-hyoid groove), along which the mylo-hyoid artery and nerve 

 pass. Behind and below this groove the medial surface of the angle is rough for 

 the attachment of the internal pterygoid muscle. Superiorly the ramus supports 

 the coronoid process in front, and the condyloid process behind, the two being 

 separated by the wide incisura mandibulae (mandibular notch), over which there pass 

 in the recent condition the vessels and nerve to the masseter muscle. The 

 coronoid process, of variable length and beak-shaped, is limited behind by a thin 

 curved margin, which forms the anterior boundary of the mandibular notch. In 

 front its anterior edge is convex from above downwards and forwards, and becomes 

 confluent below with the anterior border of the ramus and the oblique line. 

 To the medial side of this edge there is a grooved elongated triangular surface, 

 the medial margin of which, commencing above near the summit of the coronoid 

 process, leads downwards along the medial side of the root of the last molar tooth 

 towards the mylo-hyoid line. Behind this ridge the thickness of the ramus 

 is much reduced. The temporal muscle is inserted into the margins and medial 

 surface of the coronoid process. The posterior border of the ramus is continued 

 upwards to support the capitulum mandibulae (condyle), below which it is some- 

 what constricted to form the collum mandibulae (neck), which is compressed from 



