NASAL BONE. 55 



the vomer, is single, the remainder — -viz., the nasal, superior 

 maxillary, premaxillary, malar, lachrymal, palatine, pterygoid, 

 and turbinal bones, being pairs. The lower jaw is a single bone, 

 also called the inferior maxilla or mandible, and it includes 

 between its rami' the hyoid bone and its appendices. 



NASAL BONE. 

 (Fig. 10. V. ; 12. 9, 11.) 



The nasal bones are situatisd at the antero-superior part of the 

 face, immediately before the frontal bones, and between them 

 and the lachrymals and superior maxilla. They are long slender 

 bones, flattened from above downwards, somewhat triangular in 

 form, and heart-shaped when together. A nasal bone presents 

 two surfaces, two borders, a base, and an apex. 



The superior or external surface is smooth, convex from one 

 side to the other, and becomes gradually larger posteriorly. The 

 internal surface is concave, and forms the roof of the nasal fossa ; 

 a vertical ridge, to which the superior turbinal bone is attached, 

 runs along its external border ; posteriorly, this ridge bifurcates, 

 and behind and within the bifurcation is a concave surface, 

 which forms the nasal or anterior portion of the frontal sinus. 

 Above this ridge the surface is smooth, and forms a gutter, the 

 superior nasal meatus, and along the inner border is a slight 

 ridge, which combines with that of the opposite bone to form a 

 groove for the cartilaginous septum nasi. 



The internal border is straight and dentated, and articulates 

 with its fellow. The external border is very thin and waved, 

 dentated in its upper two-thirds to articulate with the lachrymal 

 bone, the superior maxilla, and the posterior part of the pre- 

 maxilla, the remaining part being free, so as to leave an angular 

 opening, the naris, between it and the premaxilla. The base 

 or superior border is rounded, serrated, and unites with the 

 frontal; the apex i% sharp and pointed, forming with its fellow 

 the nasal peak. 



The nasal bone articulates with the frontal, lachrymal, suj)erior 

 maxillary, premaxillary, and opposing nasal bones, and has the 

 superior turbinal bone attached to its inner surface. 



