THE FACE. 61 



the nose, overarching the anterior nares ; and on each side of this 

 opening the canine fossa of the superior maxillary bone and the 

 infra-orbital foramen, and still farther outwards the prominence of 

 the malar bone ; at the lower margin of the anterior nares is the 

 nasal spine, and beneath this the superior alveolar arch containing 

 the teeth of the upper jaw. Forming the lower boundary of the 

 face is the lower jaw, containing in its alveolar process the lower 

 teeth, and projecting inferiorly to form the chin ; on either side of 

 the chin is the mental foramen. If a perpendicular line be drawn 

 from the inner third of the supra-orbital ridge to the inner third of 

 the body of the lower jaw, it will be found to intersect three open- 

 ings ; the supra-orbital, infra-orbital, and mental, each giving 

 passage to one of the facial branches of the fifth nerve. 



ORBITS. 



The orbits are two quadrilateral hollow cones, situated in the 

 upper part of the face, and intended for the reception of the eye- 

 balls, with their muscles, vessels, and nerves, and the lachrymal 

 glands. The central axis of each orbit is directed outwards, so 

 that the axes of the two continued into the skull through the optic 

 foramina, would intersect over the middle of the sella Turcica.* 

 The superior boundary of the orbit is formed by the orbital plate of 

 the frontal bone, and by part of the lesser wing of the sphenoid ; 

 the inferior, by part of the malar bone and by the orbital processes 

 of the superior maxillary and palate bone; the internal by the 

 lachrymal bone, the os planum of the ethmoid and part of the 

 body of the sphenoid ; and the external, by the orbital process of 

 the malar bone and the great ala of the sphenoid ; these may be 

 expressed more clearly in a tabular form : 



Frontal. 

 Sphenoid (lesser wing). 



Malar. 

 Sphenoid (greater wing). 



Orbit. 



Lachrymal. 



Ethmoid (os planum). 



Sphenoid (body). 



Malar. 



Superior maxillary. 

 Palate. 



There are nine openings communicating with the orbit: the 

 optic, for the admission of the optic nerve and ophthalmic artery ; 

 the sphenoidal fissure, for the transmission of the third, fourth, the 

 three branches of the ophthalmic division of the fifth, and the sixth 

 nerve, and the ophthalmic vein ; the spheno-maxillary fissure, for the 

 passage of the superior maxillary nerve and artery to the opening 

 of entrance of the infra-orbital canal; temporo-malar foramina 

 two or three small openings in the orbital process of the malar 



* The axes of the orbits form an angle of 90 with each other. G. 



