THE NOSE 229 



the ethmoid and the inferior turbinate bone project inwards 

 from the outer wall, dividing each fossa into a superior, a 

 middle, and an inferior meatus. 



Openings : 



Superior meatus : sphenoidal and posterior ethmoidal cells. 



Middle meatus : anterior ethmoidal cells and frontal sinus, 

 by a common orifice the infundibulum, and antrum of High- 

 more. 



Inferior meatus : nasal duct. 



The septum is the partition separating the two fossae. It is 

 formed by the perpendicular plate of the ethmoid, the vomer, 

 crest of nasal bones, the nasal spine of the frontal, the rostrum 

 of the sphenoid, the crests of the superior maxillary and palate 

 bones, and the cartilage of the septum. The space between 

 the anterior nares and the anterior edge of the cartilage of the 

 septum is filled by membrane, the columna nasi. 



The anterior nares are the anterior openings of the nasal 

 fossae. They are separated from each other by the columna 

 nasi, and within the margin are arranged short stiff hairs, 

 vibrissa. 



The posterior nares open backwards into the pharynx. 

 They are oval in shape, being about I inch vertically and 

 inch transversely. 



Sinuses. The nasal fossae communicate with the following 

 sinuses in the neighbouring bones, the mucous membrane 

 of the nose being continued into them : 



r. Sphenoidal sinus. 



2. Posterior ethmoidal cells. 



3. Anterior ethmoidal cells. 



4. Frontal sinus. 



5. Maxillary antrum. 



The mucous membrane lining the cavity of the nose is called 

 the Schneiderian membrane. It is continuous with that of 

 the various sinuses communicating with the nasal fossae, with 

 the conjunctiva through the nasal duct and lachrymal 

 canals, with the mucous membrane of the pharynx through 

 the posterior nares, and with the skin of the face through 

 the anterior nares. On the outer wall, as on the septum, the 

 mucous membrane is inappreciably divided into an upper, 

 olfactory, and a lower, respiratory, part ; the olfactory part 

 consists of the mucosa over the superior and upper part of 

 the middle turbinated, the corresponding part of the septum 

 and the roof of the nose ; the remainder being respiratory. 



The epithelium covering the surface consists of three 

 varieties : 



