NASAL FOSSAE. 437 



5. The Mucous membrane, lining the interior of the nose, is con- 

 tinuous with the skin externally, and with the pituitary membrane 

 of the nasal fossge within. Around the entrance of the nostrils it is 

 provided with numerous vibrisscB. 



6. Vessels and Nerves. The Arteries of the nose are the lateralis 

 nasi from the facial, and the nasalis septi from the superior'coro- 

 nary. 



Its Nerves are the facial, infra-orbital, and nasal branch of the 

 ophthalmic. 



NASAL FOSSJE. 



To obtain a good view of the nasal fosses, the face must be di- 

 vided through the nose by a vertical incision, a little to one side of 

 the middle line. 



The Nasal fosses are two irregular, compressed cavities, extend- 

 ing backwards from the nose to the pharynx. They are bounded 

 superiorly by the sphenoid and ethmoid bones. Inferiorly by the 

 hard palate ; and in the middle line they are separated from each 

 other by a bony and fibro-cartilaginous septum. A plan of the 

 boundaries of the nasal fossae will be found at page 62. 



Upon the outer wall of each fossa, in the dried skull, are three 

 projecting processes, termed spongy bones. The two superior belong 

 to the ethmoid, the inferior is a separate bone. In the fresh fossae 

 these are covered with mucous membrane, and serve to increase its 

 surface by their projection and by their convoluted form. The space 

 intervening between the superior and middle spongy bones is the 

 superior meatus ; the space between the middle and inferior bones 

 is the middle meatus ; and that between the inferior and the floor of 

 the fossa is the inferior meatus. 



These meatuses are passages which extend from before backwards, 

 and it is in rushing through and amongst these that the atmosphere 

 deposits its odorant particles upon the mucous membrane. There 

 are several openings into the nasal fossae : thus, in the superior 

 meatus are the openings of the sphenoidal and posterior ethmoidal 

 cells, in the middle the anterior ethmoidal cells, the frontal sinuses, 

 and the antrum maxillare ; and, in the inferior meatus, the termina- 

 tion of the nasal duct. In the dried bone there are two additional 

 openings, the spheno-palatine and the anterior palatine foramen; the 

 former being situated in the superior, and the latter in the inferior 

 meatus. 



The Mucous membrane of the nasal fossae is called pituitary, or 

 Schneiderian.* The former name being derived from its secretion, 

 the latter from Schneider, who was the first to show that the secre- 

 tion of the nose proceeded from the mucous membrane, and not 

 from the brain, as was formerly imagined. It is continuous with 

 the general gastro-pulmonary mucous membrane, and may be traced 



* Conrad Victor Schneider, Professor of Medicine at Wittenberg. His work,' en- 

 titled De Catarrhis, &c. was published in 1661. 





