66 ATLAS AND TEXT-BOOK OF HUMAN ANATOMY. 



Fig. 73. — The osseous nasal septum seen from the left side. The frontal, sphenoid, maxilla, and palate 

 bones, and also the lamina cribrosa of the ethmoid and the ala vomeris, have been sawed 

 through close to the median line. The ethmoid is yellow, the vomer (except the cut sur- 

 face of the ala) pink. 



Fig. 74. — The vomer seen from behind (\). 



Fig. 75. — The vomer seen from the side (y). 



Fig. 76.— The right maxilla seen from the inner surface ( T ). 



Fig. 77. — The right maxilla seen from the outer surfaced). 



the sphenoidal process of the palate bone (see page 70) are applied to their margins. 

 The posterior border of the vomer forms the septum choanarum; the narrow 7 anterior border 

 articulates with the cartilaginous septum of the nose and the anterior portion of the nasal crest 

 of the maxilla; the superior border is attached to the perpendicular plate of the ethmoid; and 

 the inferior one is firmly fixed to the nasal crests of the maxilla and palate bone (Fig. 73). 



The vomer arises during the third month of fetal life as two plates situated one on either side of the upper part of 

 the cartilaginous septum of the nose, which subsequently disappears, so that the two plates become adherent after 

 birth, with the exception of the alac, which remain separated throughout life. 



THE MAXILLA. 



The maxilla (Figs. 76, 77, and 79) is a paired bone which forms the center of the facial 

 skeleton, all portions of which are more or less intimately connected with it. It assists in the 

 formation of the orbit and forms a considerable portion of the nasal fossa? and of the roof of the 

 mouth. 



It consists of a body and of four processes, the frontal or nasal process, the zygomatic process, 

 the palatine process, and the alveolar process. Of these, the alveolar process is directed downward 

 and the frontal process upward, while the zygomatic and palate processes extend in the hori- 

 zontal plane, the former externally, the latter internally. 



The body of the maxilla is irregularly cubical, and contains a large cavity, the maxillary 

 sinus (Figs. 76, 79, 97, and 98), also known as the antrum 0} Highmore. In the body there may 

 be recognized four surfaces: the anterior, the nasal, the orbital, and the infratemporal. 



The actual facial surface of the bone, the anterior surface (Fig. 77), is convex, and its 

 superior border forms a portion of the infraorbital margin. - Below this margin is an irregular 

 rounded opening, the infraorbital foramen (Figs. 37, 38, and 77), which gives exit to the vessels 

 and nerves of the same name and is the termination of the infraorbital canal. Below the infra- 

 orbital foramen there is a depression, the canine fossa, which gives origin to the musculus caninus 

 (levator anguli oris). The anterior border of the facial surface forms a portion of the lateral 

 boundary of the apertura piriformis (anterior nares), and at the infraorbital margin the surface 

 becomes continuous with the triangular orbital surface, which articulates with the lachrymal, 

 zygomatic, and ethmoid bones, but is separated from the greater wing of the sphenoid by the 

 inferior orbital (sphenomaxillary) fissure (Figs. 95, 96, and 97). This is a smooth surface; 

 it assists in forming the floor of the orbit, and exhibits a gradually deepening groove, the infra- 

 orbital groove (Fig. 96), along which there is frequently to be observed an infraorbital suture. 



