61 THE BONES. 



which articulates with a similar border on the palatine process of the opposite 

 side. 



Borders. — The anterior, thin and convex, is divided into two parts : an 

 inferior, which is mortised to receive the external border of the nasal bone and 

 the external process of the premaxilla ; and a superior, cut in a wide bevel, at 

 the expense of the external plate, to respond to the lachrymal and zygomatic 

 bones. The external border is very thick, and hollowed into six large quadrilateral 

 cavities, named alveoli, in which are implanted the molar teeth. Above the last 

 alveolus it forms a rugged eminence designated the alveolar tuberosity ; below the 

 first alveolus it becomes thin and sharp, and constitutes part of the interdental 

 space {diastema) which separates the molar from the incisor teeth. 



Extremities. — The superior is the thickest, and represents a smooth rounded 

 protuberance, into the interior of which the maxillary sinus is prolonged. Above 

 and within this eminence is a wide and deep excavation, in the formation of 

 which the palate bones participate. This is the maxillary hiatus, situated directly 

 opposite the orbital hiatus. At the bottom of this cavity is seen the nasal 

 foramen, as well as the upper orifice of the infra-orbital and the palatine 

 canals. The nasal foramen belongs to the palate bone, and enters the nasal cavity. 

 The infra-orhital cayial traverses the maxillary sinus in passing above the 

 roots of the molar teeth, and terminates by two branches — one, short and 

 wide, which opens on the external surface of the bone, on a level with the 

 third molar ; the other, very narrow, continues the course of the canal in the 

 substance of the bone, and is prolonged by several small, very fine branches 

 into the premaxillary bone. The palatine canal, channeled between the super- 

 maxillary and the palate bone, extends from the maxillary hiatus to the palatine 

 fissure. 



The inferior extremity presents a cavity which forms the alveolus of the tusk, 

 by uniting with a similar space in the premaxillary bone. 



Structure and develojyment. — This bone is developed from a single nucleus, and 

 is the more spongy- — particularly towards the alveolar border and the superior 

 extremity — as the animal is young. 



Differential Characters in the Superior Maxillary Bone of the other Animals. 



A. Ox, Sheep, Goat. — In the Ox, Sheep, and Goat, the maxillary spine does not directly 

 join the zygomatic crest ; a curved line, with concavity posterior, effects the union between 

 these two parts. The inferior oriiice of the infra-orbital foramen is pierced above the first 

 molar tooth. There is no fissure for the formation of the palatine canal. Tlie cavity of the 

 sinus is more spacious than in the Horse, and is prolonged (in the Ox only) between the two 

 laminae of the palatine roof. There is no alveolus for the tusk. 



B. Camel. — Not so long or wide as in the Horse and Ox, the supermaxilla of the 

 Camel is deeply excavated iibove the forehead and the orbit. The maxillary spine is replaced 

 by a round and i?mooth prominence, which disappears at the inferior opening of the superior 

 dental canal, pierced above the interval separating the second from the third molar. The 

 posterior face of the palatine process is narrow, has no palatine fissure, but shows the orifice 

 of the palatine canal. 



C. Pig. — In the Pig, the external surface of this bone is hollowed in its middle, and 

 presents in front a voluminous relief formed by the alveolus of the canine tooth. The cavity 

 is entirely formed in the supermaxilla. There is no alveolar tuberosity, and the interdental 

 spaoe is very short, while the cavity for the sinus is little developed. The lower orifice of the 

 palatine canal is even pierced in the substance of the supermaxilla. 



D. — Dog, Cat. — In Carnivora, this bone is very short; its anterior border offers a long 

 process analogous to the nasal spiiie of Man. It alone furnishes the alveolus of the tusk. 

 The palatine canal, pierced entirely in the bone of that name, nevertheless opens, by its 



