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OSTEOLOGY. 



THE VOMER. 



The Vomer is a single bone, situated vertically at the back part of the nasal 

 fossas, forming part of the septum of the nose. It is thin, somewhat like a 

 ploughshare in form ; but it varies in different individuals, being frequently bent 



to one or the other side; it 



Fig. 55. Vomer. presents for examination two 



surfaces and four borders. 

 The lateral surfaces are smooth, 

 marked with small furrows for 

 the lodgment of bloodvessels, 

 and by a groove on each side, 

 sometimes a canal, the naso- 

 palatine, which runs obliquely 

 downwards and forwards to 

 the intermaxillary suture be- 

 tween the two anterior palatine 

 canals; it transmits the naso- 

 palatine nerve. The superior 

 border, the thickest, presents 

 a deep groove, bounded on 

 each side by a horizontal pro- 

 jecting ala of bone ; the groove 



receives the rostrum of the sphenoid, whilst the ala3 are overlapped and retained 

 by laminae (the vaginal processes) which project from the under surface of the 

 body of the sphenoid at the base of the pterygoid processes. At the front of the 

 groove a fissure is left for the transmission of bloodvessels 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 laminaB of bone, between which is received the perpendicular 

 plate of the ethmoid, the lower half consisting of a single rough edge, also occa- 

 sionally channelled, which is united to the triangular cartilage of the nose. The 

 posterior border is free, concave, and separates the nasal fossas behind. It is 

 thick and bifid above, thin below. 



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

 by a 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 vertebrae, the coalescence of the 

 laminas taking place from behind forwards, but is not complete until after puberty. 



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

 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 BOXE. 



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

 for the reception of the inferior teeth. It consists of a curved horizontal portion, 

 the body, and of two perpendicular portions, the rami, which join the former 

 nearly at right angles behind. 



The Horizontal portion or body (fig. 56), is convex in its general outline, and 

 curved somewhat like a horseshoe. It presents for examination two surfaces 

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

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

 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 



