66 OSTEOLOGY. 



SUPERIOR MAXILLA. 



(Fig. 12. 8; Fig. 13. 14.) 



This is situated at the side of the face, and is the largest bone 

 of the upper jaw, very irregular in form, and elongated from 

 before backwards. It presents three surfaces, three borders, and 

 two extremities. 



The external or facial surface, concavo-convex in the adult, and 

 somewhat convex in the young animal, is almost smooth, having 

 an elongated horizontal ridge, the Tnaxillary spine, continuous 

 with the zygomatic spine of the malar bone, commencing opposite 

 the third molar tooth, and running along the middle line of the 

 j)osterior part of the surface. Near the middle of the upper surface 

 is the large infra-orbital foramen, through which the facial division 

 of the fifth nerve and a branch from the superior dental artery 

 pass. The inferior or palatine surface, slightly hollowed from 

 side to side, consists of a bony plate, the palatine process, which 

 forms the greater part of the bony palate, or partition between 

 the nasal fossee and the mouth ; it contains numerous small 

 grooves and foramina, and one deep groove near its outer edge, 

 the ijcdatine, which is bounded by the alveolar processes of the 

 molar teeth, and runs the whole length of the bone, giving 

 passage to the palatine artery. The internal or nasal surface 

 forms the sides and most of the floor of the nasal cavity ; it is 

 irregularly concave, smooth, and divided into two concavities by 

 a longitudinal ridge, the internal maxillary spine, to which the 

 inferior turbinal bone is attached. At the posterior part of this 

 surface is a large, deep excavation, the maxillary sinus, below 

 which is a serrated surface, articulating with the palatine bone, 

 and containing a fissure, which, with a corresponding fissure in 

 the palatine bone, forms the palatine foramen. A little anterior 

 to the sinus is the opening of the lachrymal conduit, which is 

 continued by a shallow fissure to the anterior extremity of the 

 bone ; along this conduit and fissure passes the lachrymal duct, 

 which conveys the tears from the eye to the nasal chamber. 



The superior border is thin, convex, and divided into two 

 parts — an interior, grooved and serrated for the attachment of 

 the external border of the nasal bone, and the inferior part of 

 the premaxilla, and a posterior, which is bevelled to articulate 

 with the lachrymal and malar bones. The inferior border is 



