THE BONES OF THE HEAD 



107 



Varieties. — ^The bone may persist in two parts connected by a suture, which 

 ma)' be horizontal or vertical. It sometimes persists in three parts. 



Ossification. — ^The malar is developed in membrane from three centres. 

 which appear in the eighth week of intra-uterine life, and they unite at the 

 end of the fourth month. These centres are called premalar, postmalar, and 

 hypomalar. If all three centres should fail to unite, then a tripartite malar 

 is the result. If the premalar and postmalar unite, and the h5rpomalar remains 

 separate, a bipartite malar persists with a horizontal suture. If the postmalar 

 and hjrpomalar unite, and the premalar remains separate, the suture is vertical. 

 A bipartite malar occurs with great frequentcy amongst the Japanese, and 

 from this cuncumstance the bone is known as the os Japooieam. 



The Nasal Bones. 



The nasal bone, which articulates with its fellow by its mesial 

 border, forms with it the bridge of the nose. It Hes in front of 

 the nasal process of the superior maxilla, where it enters into the 

 formation of the face and nasal fossa. The bone is elongated from 

 above downwards, and presents two sur- 

 faces and four borders. The anterior or 

 facial surface is smooth, concavo-convex 

 from above do\Miwards, and convex from 

 side to side. Near its centre it usually 

 presents a minute foramen for the passage 

 of a small vein from the nose to the com- 

 mencement of the facial vein. This surface 

 supports the common aponeurosis of the 

 pyramidalis nasi and compressor naris 

 muscles. The posterior or nasal surface is 

 rough superiorly, where it articulates with 

 the nasal process of the frontal. Elsewhere 

 it is smooth and concave from side to side, 

 and in the recent state is covered by the 

 nasal mucous membrane. It is traversed 

 longitudinally near the centre by the nasal 

 groove for the nasal ner\-e. 



The superior border is short, thick, 

 and serrated for the nasal notch of the 

 frontal: The inferior border is thin and ex- 

 panded for the upper lateral nasal cartilage. 

 It usually presents the nasal notch, which 

 is situated near its inner end. The mesial 

 border articulates with its fellow. It is 

 usually rather shorter and thicker than the 

 external, and projecting backwards from it 

 is a ledge of bone, which, wdth its fellow, 

 forms the nasal crest for articulation with the nasal spine of the 

 frontal and the anterior border of the perpendicular plate of the 

 ethmoid. The external border, long and thin, is finely serrated for 

 the nasal process of the superior maxilla. 



,, Superior Border 



— Mesial Botder 



— Nasal Notch 



Inferior Botdet 



Nasal Crest 



1 — Nasal Groove 



Fig. 65.— The Right 

 Nasal Bone. 



A, Anterior View; B. Pos- 

 terior View. 



