76 SUPERIOR MAXILLARY BOIVES. 



\vith the palate, ethmoid, and lachrymal bone ; posteriorly, by tne smooth 

 border which enters into the formation of the spheno-maxillary fissure ; 

 and, anteriorly, by a convex margin, partly smooth and partly rough, the 

 smooth portion forming part of the lower border of the orbit, and the 

 rough articulating with the malar bone. The middle of this surface is 

 channelled by a deep groove and canal, the infra-orbital, which termi- 

 nates at the infra-orbital foramen ; and near the root of the nasal process 

 is a slight depression, marking the origin of the inferior oblique muscle of 

 the eyeball. 



The four processes of the superior maxillary bone are the nasal, malar, 

 alveolar, and palate. 



The nasal process ascends by the side of the nose, to which it forms the 

 lateral boundary, and articulates with the frontal and nasal bon-e. By its 

 external surface it gives attachment to the levator labii superioris alseque 

 nasi, and to the orbicularis palpebrarum muscle. Its internal surface con- 

 tributes to form the inner wall of the nares, and is marked transversely by 

 a horizontal ridge (crista turbinalis superior) which divides it into two 

 portions, one above the ridge, irregular and uneven, for giving attachment 

 to and completing the cells of the lateral mass of the ethmoid ; the other 

 below, smooth and concave, corresponding with the middle meatus. The 

 posterior border is thick, and hollowed into a groove for the nasal duct. 

 The margin of the nasal process, which is continuous with the lower 

 border of the orbit, is sharp and marked by a small tubercle which serves 

 as a guide to the introduction of the knife in the operation for fistula 

 lachrymalis. 



The malar process , large and irregular, is situated at the angle of sepa- 

 ration between the facial and zygomatic surfaces, and presents a triangular 

 surface for articulation with the malar bone. 



The alveolar process forms the lower margin of the bone ; it is spongy 

 and cellular in texture, and excavated into deep holes for the reception 

 of eight teeth. 



The palate process is thick and strong, and projects horizontally inwards 

 from the inner surface of the body of the bone. Superiorly, it is concave 

 and smooth, and forms the floor of the nares ; inferiorly, it is also concave 

 but uneven, and assists in the formation of the roof of the palate. This 

 surface is marked by a deep groove, which lodges the posterior palatine 

 nerve and artery. Its internal edge is raised into a ridge (crista nasalis), 

 which, with a corresponding ridge in the opposite bone, forms a groove 

 for the reception of the vomer. The prolongation of this ridge forwards 

 beyond the level of the facial surface of the bone is the nasal spine. At 

 the anterior extremity of its nasal surface is a foramen, which leads into a 

 canal formed conjointly by the two superior maxillary bones, the anterior 

 palatine canal. The termination of this canal is situated immediately 

 behind the incisor teeth, hence it is also named the incisive foramen. 

 Associated with the incisive openings and canal are two smaller canals, 

 the naso-palatine, which transmit the naso-palatine nerves. These canals 

 are situated in the walls of the incisive canal, and terminate inferiorly in 

 that canal, either by separate openings or conjoined. 



Development. By four centres : one for the anterior part of the palate, 

 and incisive portion of the alveolar process (the permanence of this piece 

 constitutes the intermaxillary bone of animals) ; one for that portion of the 

 oone lying internally to the infra-orbital canal and foramen ; one for that 



