212 BOKES OF THE FACE. 



Its internal surface has, in the centre, the posterior mental 

 or inferior dental foramen, which transmits the inferior 

 dental artery and nerve. This foramen is protected by a 

 shelf of bone to which is attached the internal lateral liga- 

 ment, and it leads to a canal which passes beneath the 

 alveolar cavities, with each of which it communicates, and 

 conducts to the teeth their nerves and vessels. Below this 

 posterior foramen is the insertion of the pterygoideus inter- 

 nus muscle. The ramus terminates above in two processes, 

 viz : the anterior or coronoid, and posterior or condyloid. 



The coronoid process is triangular and is surrounded by 

 the tendinous insertion of the temporal muscle. The ante- 

 rior border of the root is grooved for the buccinator muscle. 

 The condyloid process is oblong and has its greatest diam- 

 eter looking obliquely backwards and inwards. Its upper 

 surface is smooth and covered with a movable fibro-carti- 

 lage, intervening between it and the glenoid cavity of the 

 temporal bone with which it articulates. Around the base 

 of the condyle there is a contraction called its neck, to the 

 anterior and inner portion of which the pterygoideus exter- 

 nus muscle is inserted. The curve between the two pro- 

 cesses is the sigmoid notch, over which pass the masseteric 

 artery and nerve. 



The structure of the lower jaw is compact externally, and 

 spongy or cellular within. The walls of the alveoli and 

 their partitions are also spongy. The interior of this bone 

 has already been stated to be traversed by the inferior 

 maxillary or dental canal. This canal, commencing at 

 the posterior dental foramen, gradually contracts as it 

 proceeds forwards under the summits of the alveoli. At 

 the second bicuspid tooth it divides into two canals, the one 

 large, terminating at the anterior mental foramen, the 

 other small and continued forward in the line of the 

 original canal, to the incisor teeth, to which it is dis- 

 tributed. 



The situation of this canal varies at different periods of 

 life. In the infant, at birth, according to Cruveilhier, it 

 occupies the lowest portion of the jaw. After second den- 



