90 ORBITS NASAL FOSSAE. 



ORBITS. 



The orbits are two quadrilateral hollow cones, situated in the uppei 

 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 axis 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 pro- 

 cesses 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). 



Inner wall. 



Lachrymal. 



Ethmoid (os planum). 



Sphenoid (body). 



Orbit. 



iv all. 

 Malar. 

 Sphenoid (greater wing). 



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 nerve, the sixth nerve, and the ophthalmic 

 vein ; the spheno-maxillary fissure, for the passage of the superior maxil- 

 lary nerve and artery to the opening of entrance of the infra-orbital canal ; 

 temporo-malar foramina two or three small openings in the orbital pro- 

 cess of the malar bone, for the passage of filaments of the orbital branch 

 of the superior maxillary nerve ; anterior and posterior ethmoidal foramina 

 in the suture between the os planum and frontal bone, the former trans- 

 mitting the nasal nerve and anterior ethmoidal artery, the latter the poste- 

 rior ethmoidal artery and vein; the opening of the nasal duct; and the 

 supra-orbital notch or foramen, for the supra-orbital nerve and artery. 



NASAL FOSSJE. 



The nasal fossaB are two irregular cavities, situated in the middle of the 

 face, and extending from before backwards. They are bounded above by 

 the nasal bones, ethmoid, and sphenoid : below by the palate processes of 

 the superior maxillary and palate bones ; externally by the superior maxil- 

 la;y, lachrymal, inferior turbinated, superior and middle turbinated bones 

 of the ethmoid, palate, and internal pterygoid plate of the sphenoid ; and 

 the two fossae are separated by the vomer and the perpendicular lamella 

 of the ethmoid. These may be more clearly expressed in a tabular 

 form : 



