198 BONES OP THE FACE. 



alar cartilage. The posterior is round, and forms the inner 

 border of the orbit, and immediately posterior to this bor- 

 der is a deep groove, the lachrymal fossa, for the nasal duct. 

 Its anterior surface has the orbicularis palpebarum and 

 levator labii superioris alceque nasi muscles attached to it. 

 Its internal surface forms part of the nares. The canine 

 fossa is bounded externally by a rough, serrated surface, 

 the malar process, which is concave and smooth behind for 

 receiving the temporal muscle. 



From between the nasal and malar processes, and pro- 

 jecting backwards, so as to form the floor of the orbit, is 

 the superior or orbital surface or process. This surface has 

 a triangular form; its base is internal and connected with 

 the unguiform, ethmoid, and palate bones. Its posterior 

 border helps to form the splieno-maxillary fissure. Its ex- 

 ternal unites with the malar bone, and its middle surface 

 is channeled into a canal, the infra-orbital canal, which 

 terminates in the infra-orbital foramen. This process is a 

 very thin plate of bone forming the roof of the antrum as 

 well as the floor of the orbit. The infra orbital canal, at 

 its anterior part, divides into a smaller canal, the anterior 

 dental, which descends in the anterior wall of the antrum 

 to the anterior alveoli. 



The posterior surface of the superior maxillary bone is 

 posterior and below the orbital. Its most prominent feature 

 is the tuberosity, which is larger in the young subject, as it 

 then contains the last molar tooth, and has three or four 

 small foramina, called the posterior dental canals, which 

 lead to the posterior alveoli, and transmit to the molar 

 teeth the posterior dental nerves and arteries. The infe- 

 rior portion of the tuberosity presents a rough surface for 

 articulation with the palate bone, and above and to the 

 inner side of this point of articulation, is a smooth canal, 

 which forms a portion of the posterior palatine canal. 



The inferior or palatine surface of the upper jaw consti- 

 tutes the floor of the nostrils and the roof of the mouth, 

 which corresponds in situation to the inter-maxillary bones 

 of inferior animals. 



