THE TOMER. 



169 



and veins. In the recent state it is covered by the lining membrane of the 

 nose. The external surface is concave (Fig. 121), and forms part of the inferior 

 meatus. Its upper border is thin, irregular, and connected to various bones 

 along the outer wall of the nose. It may be divided into three portions ; of 

 these, the anterior articulates with the inferior turbinated crest of the superior 

 maxillary bone; the posterior with the inferior turbinated crest of the palate 

 bone ; the middle portion of the superior border presents three well-marked 

 processes, which vary much in their size and form. Of these, the anterior and 

 smallest is situated at the junction of the anterior fourth with the posterior 

 three-fourths of the bone ; it is small and pointed, and is called the lachrymal 

 process, for it articulates with the anterior inferior angle of the lachrymal bone, 

 and by its margins, with the groove on the back of the nasal process ot the 

 superior maxillary, and thus assists in forming the lachrymal canal. At the 

 junction of the two middle fourths of the bone, but encroaching on its posterior 

 fourth, a broad thin plate, the ethmoidal process, ascends to join the unciform 

 process of the ethmoid: from the lower border of this process a thin 'lamina 

 of bone curves downwards and outwards, hooking over the lower edge ot the 

 orifice of the antrum, which it narrows below : it is called the maxillary process, 

 and fixes the bone firmly on to the outer wall of the nasal fossa. The inferior 

 border is free, thick, and cellular in structure, more especially in the middle 

 of the bone. Both extremities are more or less narrow and pointed. If the 

 bone is held so that its outer concave surface is directed backwards (i.e., towards 

 the holder), and its superior border, from which the lachrymal and ethmoidal 

 processes project, upwards, the lachrymal process will be directed to the side 

 to which the bone belongs. 



Development. By a single centre which makes its appearance about the 

 middle of foetal life. 



Articulations. With four bones ; one of the cranium, the ethmoid, and tihree 

 of the face, the superior maxillary, lachrymal, and palate. 



No muscles are attached to this bone. 



THE VOMER. 



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

 fossae, 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 presents 

 for examination two surfaces 

 and four borders. The lateral 

 surfaces are smooth, marked 

 by small furrows for the lodg- 

 ment of bloodvessels, and by 

 a groove on each side, some- 

 times a canal, the naso-pala- 

 tine, which runs obliquely 

 downwards and forwards to 

 the intermaxillary suture be- 

 tween the two anterior pala 

 tine canals; it transmits the 



, . 7 m i 



naso-palatme nerve. The su- 

 perior border, the thickest, 



presents a deep groove, bounded on each side by a horizontal projecting ala of 

 bone: the groove receives the rostrum of the sphenoid, whilst the alee 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 pro- 

 cesses. At the front of the groove a fissure is left for the transmission of blood- 



Fig. 122. Yomer. 



