98 MAXILLA INFERIOR. 



approaches the alveoH of the last molar teeth ; where it termi- 

 nates in an oblong protuberance. To the anterior part of this 

 line the mylo-hyoidei muscles are attached ; and to the posterior 

 extremity, the superior constrictor of the pharynx. The surface 

 of the bone above this ridge is smooth, and covered with the 

 gums and lining membrane of the mouth. The surface below 

 the posterior part of the line is rather concave, to accommodate 

 the submaxillary gland. 



At a small distance behind the alveoli, and nearly on a line 

 with them, midway between the roots of the two processes, is 

 a large foramen, called the inferior dental, for transmitting the 

 third, or inferior maxillary branch of the fifth pair of nerves, 

 and the blood-vessels which accompany it ; the canal, which 

 commences here, terminates at the anterior foramen, already 

 described.* The surface of this canal is perforated by many 

 foramina, through which blood-vessels and nerves pass to the 

 different teeth, and to the cancelli of the bone. On the anterior 

 side of the foramen is a sharp-pointed process, from which a 

 ligament passes to the temporal bone. The nerve and vessels, 

 before they enter into this foramen, make an impression on the 

 bone ; and there is generally a small superficial groove called 

 the mylo-hyoid, which proceeds downwards from it, being made by 

 a small nerve which supplies some of the parts under the tongue. 



At the angle of the jaw, on the inside, is a remarkable rough- 

 ness, where the internal pterygoid muscle is inserted. 



The lower jaw moves like a hinge upon its condyles in the 

 glenoid cavity, when the mouth opens and shuts in the ordinary 

 way. When the mouth is opened very wide, the condyles move 

 forward upon the tubercles before the cavities : if the effort to 

 open the mouth is continued, the lower jaw is fixed in that 

 situation, and the whole head is thrown back, v/hich separates 

 the upper jaw still farther from the lower. 



The lower jaw can be projected forward without opening the 

 mouth, by the movement of both condyles, at the same time, on 

 the tubercles. 



This bone can also rotate upon one condyle, as a centre, while 



* A branch of this canal is continued forwards to the symphysis by which 

 the front teeth are supplied with vessels and nerves. — p. 



