84 



THE SKELETON. 



which bounds this surface in front and separates it from the internal surface ia 

 attached the Dilator naris posterior. 



The posterior or zygomatic surface is convex, directed backward and outward, 

 and forms part of the zygomatic fossa. It is separated from the facial surface by 

 a strong ridge of bone, which extends upward from the socket of the second molar 

 tooth. It presents about its centre several apertures leading to canals in the 

 substance of the bone; they are termed the posterior dental canals, and transmit 

 the posterior dental vessels and nerves. At the lower part of this surface is a 

 rounded eminence, the maxillary tuberositi/, especially prominent after the growth 

 of the wisdom-tooth, rough on its inner side for articulation with the tuberosity 

 of the palate bone, and sometimes with the external pterygoid plate. It gives 

 attachment to a few fibres of origin of the Internal pterygoid muscle. Imme- 

 diately above this is a smooth surface, which forms the anterior boundary of the 

 spheno-maxillary fossa; it presents a groove which, running obliquely downward, 

 is converted into a canal by articulation with the palate-bone, forming the posterior 

 palatine canal. 



The superior or orbital surface is thin, smooth, triangular, and forms part of 

 the floor of the orbit. It is bounded internally by an irregular margin which 

 in front presents a notch, the lachrymal notch, which receives the lachrymal bone ; 

 in the middle articulates with the os planum of the ethmoid, and behind with the 

 orbital process of the palate bone ; bounded externally by a smooth, rounded edge 

 which enters into the formation of the spheno-maxillary fissure, and which some- 

 times articulates at its anterior extremity with the orbital plate of the sphenoid ; 

 hounded in front by part of the circumference of the orbit, which is continuous 

 on the inner side with the nasal, on the .outer side with the malar, process. Along 

 the middle line of the orbital surface is a deep groove, the infraorbital, for the 

 passage of the infraorbital vessels and nerve. The groove commences at the mid- 

 dle of the outer border of this surface, and, passing forward, terminates in a canal, 

 which subdivides into two branches. One of the canals, the infraorbital, opens 



Bone." partially closing orifice of antrum 

 marked in outline. 



Ethmoid. 



Inferior turbinated. 

 Palate. 



Anterior nasal spine. 



Bristle passed 

 through anterior 

 palatine canal. 



FIG. 50. Left superior maxillary bone. Internal surface. 



just below the margin of the orbit; the other, which is smaller, runs downward 

 in the substance of the anterior wall of the antrum ; it is called the anterior dental 

 canal, and transmits the anterior dental vessels and nerve to the front teeth of 



