THE SKELETON. 



glion, and presents little depressions for the lodgment of the palatine glands. When 

 the two superior maxillary bones are articulated together, a large orifice may be 

 seen in the middle line, immediately behind the incisor teeth. This is the anterior 

 palatine canal or fossa. This canal, as it passes through the thickness of the palate 

 process, is divided into four compartments ; that is to say, two canals branch off 

 laterally to the right and left nasal fossae, and two canals, one in front and one 

 behind, lie in the middle line. The former pair of these canals is named the 

 foramina of Stenson, and through them passes the anterior or terminal branch of 

 the descending or posterior palatine arteries, which ascend from the mouth to 

 the nasal fossae. The remaining pair of canals is termed the foramina of 

 Scarpa, and transmit the naso-palatine nerves, the left passing through the 

 anterior, and the right through the posterior, canal. On the palatal surface of 

 the process a delicate linear suture may sometimes be seen extending from the 

 an:erior palatine fossa to the interval between the lateral incisor and the canine 

 tooth. This marks out the intermaxillary or incisive bone which in some 

 animals exists permanently as a separate piece. It includes the whole thickness 

 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. One or two small 

 foramina in the alveolar margin behind the incisor teeth are occasionally seen in 

 the adult, almost constantly in the young subject. They are called the incisive 

 foramina, and transmit vessels and nerves to the incisor teeth. The upper surface 

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

 It presents the upper orifices of the foramina of Stenson and Scarpa, the former 

 being on each side of the middle line, the latter being situated in the intermaxil- 

 lary suture, and therefore not visible unless the two bones are placed in apposition. 

 The outer border of the palate process is incorporated with the rest of the bone. 

 The inner border is thicker in front than behind, and is raised above into a ridge, 

 the nasal crest, which, with the corresponding ridge in the opposite bone, forms a 

 groove for the reception of the vomer. In front this crest rises to a considerable 

 height, and this portion is named the incisor crest. The anterior margin is 

 bounded by the thin, concave border of the opening of the nose, prolonged forward 



internally into a sharp process, forming, with a similar 

 process of the opposite bone, the anterior nasal spine. 

 The posterior border is serrated for articulation with the 

 horizontal plate of the palate bone. 



Development. This bone commences to ossify at 

 a very early period, and ossification proceeds in it with 

 great rapidity, so that it is difficult to ascertain with 

 certainty its precise number of centres. It appears, 

 however, probable that it is ossified by five primary and 

 two secondary centres. The primary centres appear 

 about the seventh or eighth week ; first, one each for the 

 facial surface, the posterior part of the alveolus, and the 

 orbital plate, and a few days later one for the palate 

 process, and one for the front part of the alveolus, 

 which carries the incisor teeth, and which corresponds 

 to the pre-maxillary bone of the lower animals. All 

 these, except the last, speedily fuse, and the two 

 secondary centres, one for the nasal process and the 

 other for the malar process, appear and join the rest of 

 the bone. By the tenth week the bone consists of two 

 portions the greater part of the bone formed of six out 

 of the seven centres and the pre-maxillary portion. The 

 suture between these two portions on the palate persists till middle life, but is 

 not to be seen on the facial surface. This is believed by Callender to be due 

 to the fact that the front wall of the sockets of the incisive teeth is not formed 

 by the pre-maxillary bone, but by an outgrowth from the facial part of the 



Inferior Surface. 



FIG. 157. Development of 

 superior maxillary bone. At 

 birth. 



