THE MANDIBLE, OR LOWER JAW 



115 



Space for triangular 

 cartilage of septum. 



Rostrum of sphenoid. 



FIG. 84. Vomer in situs. 



Development. The vomer at an 

 irly period consists of two laminse, 

 ;parated by a very considerable in- 

 rval, and enclosing between them a 

 late of cartilage, the vomerine car- 

 lage, which is prolonged forward 

 > form the remainder of the septum. 

 >ssification commences, about the 

 ghth week, in the membrane at the 

 ostero-inferior part of this cartilage 

 om two centres, one on each side of 

 le middle line, which extend to form 

 le two laminse. The intervening 

 irtilaginous plate is absorbed. They 

 egin to coalesce at the lower part, 

 ut their union is not complete until 

 fter puberty. 



Articulations. With six bones two of the cranium, the sphenoid and ethmoid, and four 

 F the face, the maxillae and the two palate bones; and with the cartilage of the septum. 



The vomer has no muscles attached to it. 



With maxillae and palate. 



FIG. 85. The vomer. 



The Mandible, or Lower Jaw (Mandibula). 



The mandible, the largest and strongest bone of the face, serves for the reception 

 f the lower teeth. It consists of a curved, horizontal portion, the body, and two 

 erpendicular portions, the rami, which join the back part of the body nearly at 

 ight angles. 



The Body (corpus mandibulae] (Fig. 86). The body is convex in its general 

 utline, and curved somewhat like a horseshoe. It presents for examination 

 ,vo surfaces and two borders. 



Surfaces. The external surface is convex from side to side, concave from above 

 ownward. In the median line is a vertical ridge, the symphysis, which extends 



