INFERIOR MAXILLARY BONE. 



51 



This bone is marked by horizontal grooves and canals for vessels and 

 nerves, but not, as the turbinations of the ethmoid are, with vertical grooves 

 for the olfactory nerve. 



THE INFERIOR MAXILLARY BONE. 



The inferior maxilla, or lower jaw, is the thickest and strongest bone 

 of the face, and moves on the rest of the skull by means of a pair of 

 articular surfaces or condyles. It has the shape of an inverted arch bent 

 forwards upon itself, and consists of a middle larger and horizontal part 

 the body, and of two rami or ascending branches. 



Fig. 46. THE INFERIOR MAX- Fig> 46> 



ILLAKY BONE, FROM THE 

 RIGHT SIDE AND ABOVE. ^ 



1, the body; 2, the sym- 

 physis ; 3, the ramus ; 4, the 

 angle, near it the oblique ridges 

 marked by the attachment of 

 the masseter muscle ; 5, the 

 coronoid process ; 6, the con- 

 dyle or articular head ; 7, placed 

 in the sigmoid notch, points to 

 the front of the neck; 8, the 

 mental foramen ; 9, the external 

 oblique ridge ; 10, the inferior 

 dental foramen and mylohyoid 

 groove of the left side. This 

 figure represents a full set of 

 the teeth of the lower jaw in 

 middle life. (See also, for the 

 view of the inner surface of the lower jaw, figure 53, the vertical section of the skull.) 



The body is marked in the middle by a vertical ridge, indicating the original 

 division of the bone into two lateral parts, and thence named the sym- 

 physis. The superior or alveolar border is hollowed out into sockets for 

 the teeth. The inferior border, thicker anteriorly than beneath the ramus, 

 is slightly everted in front, constituting the chin, or mentum, a prominence 

 peculiar to the human skull. On the outer surface, on each side of the 

 symphysis, below the incisor teeth, is a shallow depression, the incisor 

 /ossa, which gives origin to the levator menti muscle, and, more externally, 

 the labial or mental foramen, which transmits the facial branches of the 

 inferior dental nerve and artery. From beneath the mental foramen an 

 elevation, the external oblique line, extends upwards and outwards to 

 the anterior border of the ramus. The deep surface is marked, on each side 

 of the symphysis, along the inferior margin, by a depression, indicating 

 the anterior attachment of the digastric muscles, and above them by two 

 pairs of prominent tubercles, spince mentales, placed closely together, giving 

 attachment, the upper pair to the genio-hyo-glossi, and the lower to the 

 genio-hyoidei muscles. An oblique prominent line, the mylo-hyoidean ridge, 

 leading from beneath the spinee mentales, upwards and outwards to the 

 ramus, gives attachment to the mylo-byoideus muscle. Above this line 

 is a smooth depression for the sublingual gland, and beneath and external 

 to it another for the submaxillary gland. 



The ramus is thinner than the body of the bone, and its border forms, 

 posteriorly and inferiorly with that of the body, an angle, called the angle 

 of the jaw. The external surface is flat and marked by slight unevenness, 

 and towards the angle by rirlges at the place of attachment of the masseter 



B 2 



