SUPERIOR MAXILLARY BONE. 



85 



The Alveolar Process is the thickest and most spongy part of the bone, broader 

 behind than in front, and excavated into deep cavities for the reception of the 

 teeth. These cavities are eight in number, and vary in size and depth according 

 to the teeth they contain : those for the canine teeth being the deepest ; those for 

 the molars being widest, and subdivided into minor cavities ; those for the incisors 

 being single, but deep and narrow. 



The Palate Process, thick and strong, projects horizontally inwards from the 

 inner surface of the bone. It is much thicker in front than behind, and forms a 

 considerable part of the floor of the nares, and the roof of the mouth. Its upper 

 surface is concave from side to side, smooth, and forms part of the floor of the 

 nose. In front is seen the upper orifice of the anterior palatine (incisor) canal, 

 which leads into a fossa formed by the junction of the two superior maxillary 

 bones, and is situated immediately behind the incisor teeth. It transmits the ante- 

 rior palatine vessels, the naso-palatine nerves passing through the intermaxillary 

 suture. The inferior surface, also concave, is rough and uneven, and forms part 

 of the roof of the mouth. This surface is perforated by numerous foramina for 

 the passage of nutritious vessels, channelled at the back part of its alveolar border 

 by a longitudinal groove, sometimes a canal, for the transmission of the posterior 

 palatine vessels, and a large nerve, and presents little depressions for the lodgment 

 of the palatine glands. This surface presents anteriorly the lower orifice of the 

 anterior palatine fossa. In some bones, a delicate linear suture may be seen 

 extending from the anterior palatine fossa to the interval between the lateral 

 incisor and the canine teeth. This marks out the intermaxillary bone, which in 

 some animals exists permanently as a separate piece. It includes the whole thick- 

 ness of the alveolus, the corresponding part of the floor of the nose, and the 

 anterior nasal spine, and contains the sockets of the incisor teeth. The outer 

 border of the palate process is 



firmly united with the rest of the Fi S- 47. Development of Superior Maxillary Bone. By 



bone. The inner border is thicker Four Centres, 



in front than behind, raised above 

 into a ridge, which, with the cor- 

 responding ridge in the opposite 

 bone, forms a groove for the re- 

 ception of the vomer. The an- 

 terior margin is bounded by the 

 thin concave border of the open- 

 ing of the nose, prolonged for- 

 wards internally into a sharp 

 process, forming, with a similar 

 process of the opposite bone, the 

 anterior nasal spine. The pos- 

 terior border is serrated for 

 articulation with the horizontal 

 plate of the palate bone. 



Development. This bone is 

 formed at such an early period, 

 and ossification proceeds in it 

 with such rapidity, that it has 

 been found impracticable hither- 

 to to determine with accuracy 

 its number of centres. It ap- 

 pears, however, probable that it has four centres of development, viz., one for the 

 nasal and facial portions, one for the orbital and malar, one for the incisive, and 

 one for the palatal portion, including the entire palate except the incisive seo-rnent. 

 The incisive portion is indicated in young bones by a fissure, which marks off a 

 small segment of the palate, including the two incisor teeth. In some animals, this 

 remains permanently as a separate piece, constituting the intermaxillary bone : and 



1 far Na.ta.1 tf 

 1'a.fial ort?} 



1 for Orlital tf 

 Malar port'? 



I for Incisive port? 



1 for Palafa 



Anterior Surface. 



at 

 Bt'rfA 



Surfuce. 



