CHAP, in.] SKELETON OF THE HEAD AND TRUNK. 73 



The maxillary bone, or MAXILLA, is the largest bone of the face, 

 forming as it does, with its fellow of the opposite side, the main 

 part of the upper jaw, and supporting all the upper teeth, except 

 the incisors. It also contributes to form the cheek, the orbit, the 

 nasal passage, and the palate. The two maxillary bones do not 

 meet in the middle line below the anterior nares, but each sends up 

 a prolongation the nasal process (n) to the frontal. This process 

 bounds the inner side of the orbit anteriorly, and by its anterior 

 and upper margin joins the nasal bone. Its inner surface exhibits 

 a vertical groove, which is made into a canal by the help of the 

 lachrymal bone. There is also on the inner surface a more or less 

 horizontal ridge which serves to give attachment to the maxillo- 

 turbinal. The superior, external part of the maxilla sends a process 

 outwards (beneath the orbit), which joins the malar bone, and is 

 therefore called the malar process (m). Superiorly the maxilla 

 exhibits a smooth, horizontal surface (Fig. 28, m) which forms the 

 floor of the orbit, and is called the orbital plate. It is traversed, 

 from before backwards, by a groove ending anteriorly in a large 

 foramen (2), which transmits the second branch of the fifth nerve, 

 and is called the infra-orbital fifth nerve. 



On the outer surface of the maxilla, in front of the malar process, 

 is a slight concavity termed the " canine fossa." Behind the malar 

 process the outer surface of the maxilla has a slightly enlarged 

 portion called the tuber osity (t), which is perforated by small 

 foramina for the superior dental nerves and arteries. The lowest 

 part of the maxilla is termed the alveolar border, and ^ is hollowed 

 out into the alveoli, or sockets, for the teeth. From this border the 

 maxilla sends inwards a large horizontal process called the palatine 

 plate. This is smooth and transversely concave above, but more or 

 less roughened and grooved below. It rises somewhat where it 

 meets its fellow of the opposite side in a sutural ridge (0), which 

 supports the vomer. The anterior margin of the palatine plate is 

 slightly, its posterior margin is deeply, concave. 



The maxilla articulates with the pre-maxilla and nasal in front, 

 with the frontal above, and with the lachrymal, malar, and palatine 

 behind. 



31. The PRE-MAXILLA is a very small bone placed in front of 

 the maxilla, and joining, anteriorly, its fellow of the opposite side 

 the two together forming the anterior termination of the upper 

 jaw. Each pre-maxilla consists of two unequal pointed processes 

 diverging, one upwards and one backwards, from a thickened 

 anterior portion which is the alveolar margin, and supports three 

 incisors. 



The ascending, and much the larger, process (m) mounts up in 

 front of, and adjacent to, the anterior margin of the ascending nasal 

 process of the maxilla as far as the nasal, insinuating itself between 

 that bone and the maxiUa. The two pre-maxilla3 bound the anterior 

 nares below and on each side, the nasals bounding the antenor nasal 

 opening above. 



