170 



THE SKELETON. 



vessels to the substance of the bone. The inferior border, the longest, is broad 

 and uneven in front, where it articulates with the two superior maxillary bones; 

 thin and sharp behind, where it joins with the palate bones. The upper half 

 of the anterior border usually consists of two laminas of bone, between which 

 is received the perpendicular plate of the ethmoid, the lower half consisting of 

 a single rough edge, also occasionally channelled, which is united to the tri- 

 angular cartilage of the nose. The posterior border is free, concave, and sepa- 

 rates the nasal fossae behind. It is thick and bifid above, thin below. 



Development. The vomer at an early period consists of two laminae separated 

 bya very considerable interval, and inclosing between them a plate of cartilage 

 which is prolonged forwards to form the remainder of the septum. Ossification 

 commences in it at about the same period as in the vertebra (the coalescence 

 ot the laminae taking place from behind forwards), but is not complete until 

 after puberty. 



Articulations. "With six bones ; two of the cranium, the sphenoid and eth- 

 moid ; and four of the face, the two superior maxillary and the two palate 

 bones, and with the cartilage of the septum. 



The vomer has no muscles attached to it. 



THE INFERIOR MAXILLARY BONE. 



The Inferior Maxillary Bone, the largest and strongest bone of the face, 

 serves for the reception of the lower teeth. It consists of a curved horizontal 

 portion, or body, and two perpendicular portions, or rami, which join the back 

 part of the body nearly at right angles. 



The Horizontal Portion, or Body (Fig. 123), is convex in its general outline, 

 and curved somewhat like a horseshoe. It presents for examination two sur- 

 faces and two borders. The external surface is convex from side to side, concave 



Fig. 123. Inferior Maxillary Bone. Outer Surface. Side View. 



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from above downwards. In the median line is a vertical ridge, the symphysis, 

 which extends from the upper to the lower border of the bone, and indicates 

 the point of junction of the two pieces of which the bone is composed at an 

 early period of life. The lower part of the ridge terminates in a prominent 

 triangular eminence, the mental process. On either side of the symphysis, just 

 below the roots of the incisor teeth, is a depression, the incisive fossa, for the 

 attachment of the Levator Menti ; and still more externally, a foramen, the 

 mental foramen, for the passage of the mental nerve and artery. This foramen 

 is placed just below the root of the second bicuspid tooth. Eunning outwards 



