NASAL FOSS.E. 613 



alas of the nose, it is thicker, and more firmly adherent. It is furnished with a 

 large numbef of sebaceous follicles, the orifices of which are usually very distinct. 



The mucous membrane lining the interior of the nose is continuous with the 

 skin externally, and with that which lines the nasal fossas within. 



The arteries of the nose are the lateralis nasi from the facial, and the nasal 

 artery of the septum from the superior coronary, which supplies the alae and 

 septum; the sides and dorsum being supplied from the nasal branch of the 

 ophthalmic and infra-orbital. 



The veins of the nose terminate in the facial and ophthalmic. 



The nerves of the nose are branches from the facial, infra-orbital, and infra- 

 trochlear, and a filament from the nasal branch of the ophthalmic. 



NASAL FOSSJS. 



The Nasal Fossae are two irregular cavities, situated in the middle of the face, 

 and extending from before backwards. They open in front by the two anterior 

 nares, and terminate behind in the pharynx, by the posterior nares. The 

 boundaries of these cavities, and the openings which are connected with them, 

 as they exist in the skeleton, have been already described (p. 109). 



The mucous membrane lining the nasal fossa3 is called pituitary, from the 

 nature of its secretion, or Schneiderian from Schneider, the first anatomist who 

 showed that the secretion proceeded from the mucous membrane, and not, as was 

 formerly imagined, from the brain. It is intimately adherent to the periosteum 

 or perichondrium over which it lies. It is continuous externally with the skin, 

 through the anterior nares, and with the mucous membrane of the pharynx, 

 through the posterior nares. From the nasal fossa3 its continuity may be traced 

 with the conjunctiva, through the nasal duct and lachrymal canals; with the 

 lining membrane of the tympanum and mastoid cells, through the Eustachian 

 tube; and with the frontal, ethmoidal, and sphenoidal sinuses, and the antrum 

 maxillare, through the several openings in the meatuses. The mucous membrane 

 is thickest, and most vascular, over the turbinated bones. It is also thick over 

 the septum ; but, in the intervals between the spongy bones, and on the floor of the 

 nasal fossa3, it is very thin. "Where it lines the various sinuses and the antrum 

 maxillare, it is thin and pale. 



The surface of the membrane is covered with a layer of tessellated epithelium, 

 at the upper part of the nasal fossa3, corresponding with the distribution of the 

 olfactory nerve, but ciliated throughout the rest of its extent, excepting near the 

 aperture of the nares. 



This membrane is also provided with a nearly continuous layer of branched 

 mucous glands, the ducts of which open upon its surface. They are most nume- 

 rous at the middle and back parts of the nasal fossas, and largest at the lower and 

 back part of the septum. 



Owing to the great thickness of this membrane, the nasal fossa3 are much 

 narrower, and the turbinated bones, especially the lower ones, appear larger, and 

 more prominent, than in the skeleton. From the same circumstance, also, the 

 various apertures communicating with the meatuses are either narrowed or 

 completely closed. 



In the superior meatus, the aperture of communication with the posterior 

 ethmoidal cells is considerably diminished in size, and the spheno-palatine foramen 

 completely covered in. 



In the middle meatus, the opening of the infundibulum is partially hidden by 

 a projecting fold of mucous membrane, and the orifice of the antrum is contracted 

 to a small circular aperture, much narrower than in the skeleton. 



In the inferior meatus, the orifice of the nasal duct is partially hidden by either 

 a single or double valvular mucous fold, and the anterior palatine canal either 

 completely closed in, or a tubular cul-de-sac of mucous membrane is continued a 

 short distance into it. 



