114 SPECIAL ANATOMY OF THE SKELETON 



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 lacrimal process (processus lacrimalis); it articulates by 

 its apex with the anterior inferior angle of the lacrimal bone, and by its margins 

 with the groove on the back of the nasal process of the maxilla, and thus assists 

 in forming the canal for the nasal duct. At the junction of the two middle fourths 

 of the bone, but encroaching on its posterior fourth, a broad, thin plate, the eth- 

 moidal process (processus ethmoidalis), ascends to join the unciform process of the 

 ethmoid; from the lower border of this process a thin lamina of bone curves down- 

 ward and outward, hooking over the lower edge of the orifice of the antrum, which 

 it narrows below; it is called the maxillary process (processus maxittaris), and fixes 

 the bone firmly to the outer wall of the nasal fossa. The inferior border is free and 

 thick, more especially in the middle of the bone. Both extremities are more or 

 less narrow and pointed, the posterior being the more tapering. If the bone is 

 held so that its outer concave surface is directed backward (i. e., toward the holder), 

 and its superior border, from which the lacrimal and ethmoidal processes project, 

 upward, the lacrimal process will be directed to the side to which the hone belongs. 1 



Development. From a single centre, which makes its appearance about the middle of fetal 

 life in the outer wall of the cartilaginous nasal septum. 



Articulations. With four bones one of the cranium, the ethmoid, and three of the face, 

 the maxilla, lacrimal, and palate. 



No muscles are attached to this bone. 



The Vomer. 



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

 fossae, forming part of the septum of the nose (Fig 84). It is thin, somewhat like a 

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

 one or the other side; it presents for examination two surfaces and four borders. 



Surfaces. The lateral surfaces are smooth, marked by small furrows for the 

 lodgement of bloodvessels, and by a groove on each side, sometimes a canal, 

 the nasopalatine groove, or canal, which runs obliquely downward and forward to 

 the intermaxillary suture; it transmits the nasopalatine nerve. 



Borders. The superior border, the thickest, presents a deep groove, bounded 

 on each side by a horizontal projecting leaf of bone; these leaves are the alae (alae 

 vomeris). The groove formed by the alse receives the rostrum of the sphenoid, 

 while the alee are overlapped and retained by the vaginal processes, which pro- 

 ject on 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 blood- 

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

 uneven in front, where it articulates with the two maxillae; thin and sharp behind, 

 where it joins with the palate bones. The upper half of the anterior border usually 

 consists of two lamina? of bone, in the groove between which is received the per- 

 pendicular plate of the ethmoid; the lower half, also separated into two lamella?, 

 receives between them the lower margin of the septal cartilage of the nose. The 

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

 and bifid above, thin below. 



The surfaces of the vomer are covered by mucous membrane, which is inti- 

 mately connected with the periosteum, with the intervention of very little, if any, 

 submucous connective tissue. 



1 If the lacrimal process is broken off. as is often the case, the side to which the hone belong may be known 

 by recollecting that the maxillary process is nearer the back than the front of the bone. 



