THE NASAL FOSSAE. 



887 



The mucous membrane lining the nasal fossae is called the 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 fossae 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 of 

 Highmore 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 



Hiatus Ant. ethm. 



semilunaris cells 



Eye-ball 



Groove (hiatus semilunaris) 

 leading to infundibulum 

 Middle turbinated bone 



Middle meatus 

 Antrum of Highmore 

 'nferior meatus 



Inferior turbinated bone 



f Buccal cavity 



\ Space between cheek and gum 

 Molar tooth, upper jaw 



Koot of molar tooth 



^^ Inferior dental nerve 



Tunrjue I Hard palate 



Septum 

 nasi 



FIG. 524. Transverse vertical section of the nasal fossae. The section is made anterior to the superior 

 turbinated bones. (Cryer.) 



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

 nasal fossae it is very thin. Where it lines the various sinuses and the antrum of 

 Highmore it is thin and pale. 



Owing to the great thickness of this membrane, the nasal fossae 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 



