SUPERIOR MAXILLARY BONES. 41 



and lachrymal bone ; and the posterior border is irregularly cellular, 

 to articulate with the sphenoid and palate bones. 



The lateral masses are composed of cells, which are divided by a thin 

 partition into anterior and posterior ethmoidal cells. The anterior, the 

 most numerous, communicate with the frontal sinuses, and open by 

 means of an irregular and incomplete tubular canal, the infundibulum, 

 into the middle meatus. The posterior cells, fewer in number, open 

 into the superior meatus. 



Development. By three centres ; one for each lateral mass, and one 

 for the perpendicular lamella. Ossification commences in the lateral 

 masses at about the beginning of the fifth month, appearing first in the 

 os planum and then in the spongy bones. During the latter half of the 

 first year after birth, the central lamella and lamina cribrosa begin to 

 ossify, and are united to the lateral masses by the beginning of the 

 second. The cells of the ethmoid are developed in the course of the 

 fourth and fifth year. 



Articulations. With thirteen bones; two^tff th cranium, tlfev 

 frontal and sphenoid ; the rest of the face, viz. ''the nasal, superior 

 maxillary, lachrymal, palate, the inferior turbinated, and the vomer. 



No muscles are attached to this bone. 



BONES OF THE FACE. 



The face is composed of fourteen bones ; viz. the 

 Two nasal, Two palate, 



Two superior maxillary, Two inferior turbinated, 



Two lachrymal, Vomer. 



Two malar, Inferior maxillary. 



NASAL BONES. The nasal (fig. 28) are two small quadrangular 

 bones, forming by their union the bridge and base of the nose. Upon 

 the upper surface they are convex, and pierced by a foramen for a 

 small artery ; on the under surface they are somewhat concave, and 

 marked by a groove, which lodges the nasal branch of the ophthalmic 

 nerve. The superior border is narrow and thick, the inferior broad, 

 thin, and irregular. 



Development. By a single centre for each bone, the first ossific de- 

 position making its appearance at the same time as in the vertebrae. 



Articulations. With four bones ; frontal, ethmoidal, nasal, and 

 superior maxillary. 



Attachment of Muscles. It has in relation with it the pyramidalis 

 nasi, and compressor nasi; but neither of these muscles is inserted 

 into it. 



SUPERIOR MAXILLARY BONES. The superior maxillary are the 

 largest bones of the face, with the exception of the lower jaw ; they 

 form, by their union, the whole of the upper jaw, and assist in the 

 construction of the nose, the orbit, the cheek, and the palate. Each 

 bone is divisible into a body and four processes. 



