122 CAVITIES OF THE NOSE. 



surface is the partition between the antrum maxillare and the 

 orbit of the eye, and is more or less absorbed in those cases where 

 polypi of the antrum maxillare occasion a protrusion of the eye. 



The external surface, formed by the malar bone and the 

 orbitar plate of the sphenoid, is almost flat. In the posterior 

 part of the orbit it is bounded by two large fissures, which are 

 now to be described. 



In the posterior part of the orbit are three apertures. The optic 

 foramen, the sphenoidal fissure, and the spheno-maxillary fissure. 



The optic foramen opens almost at the bottom of the orbit on 

 the inside ; its direction is forwards and outwards. 



The sphenoidal fissure, formed principally by the lesser and 

 greater wings of the sphenoidal bone, begins at the bottom of 

 the orbit, and extends forward, upward, and outward. It is 

 broad at the commencement, and gradually diminishes to a fissure. 

 This fissure opens directly into the cavity of the cranium, and 

 admits the passage of the third, fourth, sixth, and one branch of 

 the fifth pair of nerves, and an artery, and a vein. 



The spheno-maxillary fissure commences also at the bottom 

 of the orbit, and extends forward, outward, and downward, 

 between the maxillary bone and the orbitar plate of the sphe- 

 noid, from the body of the sphenoid to the malar bone. This 

 fissure opens from the orbit directly into the zygomatic fossa. In 

 the recent subject it is closed, and only transmits the infra-orbi- 

 tary nerve and vessels, and a small branch of the superior 

 maxillary nerve. 



The Cavities of the Nose. 



These cavities, which are separated from each other by the 

 septum narium, are contained between the cribriform plate of 

 the ethmoid and the palatine process of the upper maxillary and 

 palate bones, and between the anterior and posterior nares. 

 They are, therefore, of considerable extent in these directions ; 

 but the distance from the septum to the opposite side of the 

 nose is so small, that each cavity is very narrow. 



The upper surface of each cavity consists of that portion of 

 the cribriform plate of the ethmoid which is between the septum 

 and the cellular portions. Anterior to this, each cavity is 



