SUPERIOR MAXILLARY BOXES. 75 



the lower margin of the orbit, continuous externally with the rough articu- 

 lar surface of the malar process, and internally with a thick ascending plate, 

 the nasal process. Towards the middle line of the face this surface is 

 bounded by the concave border of the opening of the nose, which is pro- 

 jected forwards at its inferior termination into a sharp process, forming, 

 with a similar process of the opposite bone, the nasal spine. Beneath the 

 nasal spine, and above the two superior incisor teeth, is a slight depression, 

 the incisive, or my rtiform fossa, which gives origin to the depressor labii 

 superioris' alaBque nasi muscle. The myrtiform fossa is divided from the 

 canine fossa by a perpendicular ridge, corresponding with the direction 

 of the root of the canine tooth. The inferior boundary of the facial surface 

 is the alveolar process which contains the teeth of the upper jaw ; and it 

 is separated from the zygomatic surface by a strong projecting eminence, 

 the malar process. 



The internal, or nasal surface, presents a large irregular opening, lead- 

 ing into the antrum maxillare ; this opening is nearly closed in the articu- 

 lated skull by the ethmoid, palate, lachrymal, and inferior turbinated bones. 

 The cavity of the antrum is somewhat triangular, corresponding in shape 

 with the form of the body of the bone. Upon its inner wall are numerous 

 grooves, lodging branches of the superior maxillary nerve, and projecting 

 into its floor several conical processes, corresponding with the roots of the 

 first and second molar teeth. In front of the opening of the antrum is the 

 strong ascending plate of the nasal process, marked inferiorly by a rough 

 horizontal ridge (crista turbinalis inferior), which gives attachment to the 

 inferior turbinated bone. The concave depression immediately above this 

 ridge corresponds with the middle meatus of the nose, and that below the 

 ridge with the inferior meatus. Between the nasal process arid the opening 

 of the antrum, is a deep vertical groove (sulcus lachrymalis) which is con- 

 verted into a canal by the lachrymal and inferior turbinated bone, and consti- 

 tutes the nasal duct. The superior border of the nasal surface is irregularly 

 cellular, and articulates with the lachrymal and ethmoid bone ; the poste- 

 rior border is rough, and articulates with the palate bone ; the anterior 

 border is sharp, and forms the free margin of the opening of the nose ; and 

 from the inferior border projects inwards a strong horizontal plate, the 

 palate process. 



The posterior surface may be called zygomatic, from forming part of 

 the zygomatic fossa ; it is bounded externally by the malar process, and 

 internally by a rough and rounded border, the tuberosity, which is pierced 

 by a number of small foramina (foramina alveolaria posteriora), giving 

 passage to the posterior dental nerves and branches of the superior dental 

 artery. The lower part of this tuberosity presents a rough oval surface, to 

 articulate with the palate bone, and immediately above and to the inner 

 side of this articular surface a smooth groove, which forms part of the pos- 

 terior palatine canal. The superior border is smooth and rounded to form 

 the lower boundary of the spheno-maxillary fissure, and is marked by a 

 notch, the commencement of the infra-orbital canal. The inferior boundary 

 is the alveolar process, containing the last two molar teeth. 



The orbital surface is triangular and thin, and constitutes the floor of 

 the orbit. It is bounded internally by an irregular edge, which articulates 



the lachrymal bone, and forms the commencement of the nasal duct. 15. The crista 

 nasalis of the palate process, i. The two incisor teeth, c. The canine, b. The tw? 

 bicuspidati. m. The three molarcs. 



