72 ATLAS AND TEXT-BOOK OF HUMAN ANATOMY. 



Fig. 90. — The mandible seen from in front (|). 



Fig. 91. — The mandible seen from the outer surface (|). 



Fig. 92. — The mandible seen from below ({■). 



Fig. 93. — One-half of the mandible seen from the inner surface (|). 



Fig. 94. — The hyoid bone seen from in front and above (\). 



is the mental tubercle. Above and to the outer side of the mental tubercle is situated the mental 

 joramen, giving exit to the vessels and nerve of the same name and forming the inferior opening 

 of the mandibular (inferior dental) canal, which traverses the greater portion of the body of 

 the mandible. There is also to be observed upon the outer surface of the body a smooth ridge, 

 the oblique line, which passes downward from the root of the coronoid process, gradually fades 

 away, and finally entirely disappears somewhat to the outer side of the mental foramen (Figs. 

 90 and 91). 



The internal surface of the body of the mandible (Figs. 92 and 93) exhibits, to either side 

 of the median line, a shallow depression which is known as the digastric fossa, since it received 

 the insertion of the anterior belly of the digastric muscle, and above this there is a short, rough, 

 irregular prominence, the mental spine, which is usually a paired structure and sometimes also 

 shows a further transverse subdivision; it gives origin to the geniohyoid and geniohyoglossus 

 muscles. To the outer side of the mental spine there is a larger shallow depression which lodges 

 the sublingual salivary gland, and between the sublingual and digastric fossae is the termination 

 of the rough mylohyoid line, which passes from behind forward and from above downward 

 upon the inner surface of the body of the mandible and gives origin to the mylohyoid muscle. 



A certain distance below the mylohyoid line there is a groove which commences at the 

 mandibular foramen (Figs. 92 and 93) situated upon the inner surface of the ramus, and gradu- 

 ally disappears as it passes forward; this is the mylohyoid groove and contains the vessels and 

 nerve of the same name. Below the mylohyoid line, to the outer side of the depression for 

 the sublingual gland, and frequently difficult of recognition, there is a much shallower depres- 

 sion for the submaxillary gland. 



Each ramus forms almost a right angle with the body of the bone, and is both broader and 

 thinner than the body. It passes upward, broadens, and divides into two processes, an anterior 

 coronoid and a posterior condyloid process, which are separated by the notch of the mandible 

 (the sigmoid notch). 



The ramus, like the body of the bone, possesses an external surface and an internal surface^ 

 a portion of the latter being directed toward the oral cavity. The external surface (Fig. 96) 

 is roughened at the angle, forming the masseteric tuberosity for the insertion of the masseter 

 muscle. There is a corresponding rough area upon the inner surface, the pterygoid tuberosity, 

 for the insertion of the internal pterygoid muscle. 



At about the middle of the ramus there is an opening, the mandibular {inferior dental) 

 foramen (Fig. 93), the superior opening of the mandibular {inferior dental) canal* which passes 



* The mandibular canal is continued within the bone beyond the mental foramen almost to the median line and 

 gives off small lateral ramifications which lead to the apices of the alveoli. 



