THE LACHRYMAL AM) VOMER o3 



The outer surface is concave, and overhung l)y the auricular or maxillary 

 process. The inner surface is convex and pitted with depression;^. The superior 

 border presents from l)efore liackwards three processes: the tirst is called the 

 lachrymal process, l)ecause it articulates with tlie turbinal process of the lachrymal 

 hone. The margin of bone at the l)ase of this process comes into relation with 

 the nasal process of the maxilla. The second vertical spiculuni is the ethmoidal 

 process, which joins the uncinate process of the ethmoid. The third or maxillary 

 process is a thin lamella of bone, turned downwards; it overhangs the oritice of 

 the maxillary sinus, and serves to fix the bone firmly to the outer wall of the 

 nasal fossa. The margin posterior to the maxillary process comes into relation 

 with the inferior turbinal crest of the palate bone. The inferior l)order is rounded 

 and free. It is the thickest part of the bone. The extremities are narrow, the 

 posterior ])eing the more pointed. 



Articulations. — The inferior turbinal articulates with the maxilla, lachrymal, 

 palate, and ctlimoid. 



The inferior turbinal is ossified in cartilage from a single nucleus which appears 

 about the fifth month of intra-uterine life. 



At birth it is a relatively large bone, and fills up the lower part of the nasal 

 fossa. 



THE LACHRYMAL 



The lachrymal bones are extremely thin and delicate, quadrilateral in shape, 

 and situated at the anterior part of the inner wall of the orbit. They are the 

 smallest of the facial bones. 



The outer or orbital surface is divided by a vertical ridge into two unequal 

 })ortions. The anterior smaller portion is deeply grooved to form the lachrymal 

 sulcus, which lodges the lachrymal sac and forms the commencement of the 

 lachrymal duct. The portion Ixdiind the ridge is smooth, and forms part of the 

 inner wall of the orbit. The ridge gives origin to the tensor tarsi muscle, and 

 terminates inferiorly in a hook-like process, the hamulus, which curves forwards to 

 articulate with the lachrymal tubercle of the maxilla and completes the superior 

 orifice of the lachrymal canal. The inner surface is in relation with the two 

 anterior cells of the ethmoid (lachry mo-ethmoid), and forms part of the infundi- 

 bulum. The superior l^orcler is short, and articulates with the internal angular 

 process of the frontal. The lower border posterior to the crest joins the inner edge 

 of the orbital plate of the maxilla. The narrow piece, anterior to the ridge, is 

 prolonged downwards to join the lachrymal spine of the inferior turbinal, and is 

 called the turbinal process. The anterior border comes into relation with the 

 posterior border of the nasal process of the maxilla. The posterior border articu- 

 lates with the OS planum of the ethmoid. 



Articulations. — The lachrymal articulates with the ethmoid, maxilla, frontal 

 and inferior turl)inal bones. 



Blood-supply. — Its arteries are derived from the infraorbital, the nasal l)ranch 

 of the ophthalmic, and the anterior ethmoidal. 



Ossification. — This bone arises in the membrane overlying the cartilage of the 

 fronto-nasal j)late. Its mode of ossification is very variable. As a rule it is de- 

 scribed as coming from one nucleus. Not unfrequently the hamulus is a separate 

 element. Sometimes the Ijone is divided horizontally, and a process of the os 

 planum projects between the two halves to join the nasal process of the maxilla. 

 More rarely the bone is represented by a group of detached ossicles resembling 

 Wormian l^ones. 



THE VOMER 



The vomer is an irregular four-sided plate of l)one constituting the lower i)ortion 

 of the nasal septum. It is usually described as resembling a ploughshare in shape. 

 Each lateral surface is covered by the thick nuicous membrane of the nasal sinus, 

 and is traversed by a narrow but well-marked groove, which lodges the naso- 



