THE NASAL FOSS^ 



667 



This cartilage is the persistent anterior extremity of tlie primordial 

 cranium. In young subjects it is prolonged back to the body of the 

 pre-sphenoid bone ; and in many adults an irregular thin band remains 

 between the vomer and the central plate of the ethmoid. 



NASAL FOSS.IJ. 



The nasal fosste, and the various openings into them, with the pos- 

 terior nares, have been previously described as they exist in the skeleton, 

 and the greater part of that description is also applicable generally to 

 the nose in a recent state ; but it is proper to mention certain dif- 

 ferences in the form and dimension of parts, which depend on the 

 arrangement of the lining membrane, viz. — 



Throughout the whole of the nasal fossas it is to be observed that — 

 Firstly, owing- to the thickness of the membrane in question, (which not only 

 lines the walls of the fossas, but covers the spongy bones on both sides.) the nasal 

 cavity is much narrower in the recent state. Secondly, in consequence of the 

 prolongations of membrane on their free margins, the tm-binate bones, and more 

 particularly the lower pair, appear in the recent state to be both more prominent, 

 and longer in the direction, from before backwards, than in the dried skull. 

 Thirdly, by the arrangement of the mucous membrane aroimd and over the 

 orifices which open into the nasal fossas, some of the foramina in the bones are 

 narrowed, and others completely closed. 



Fi-. 4S2. 



Fig. 482. — Transverse Vertical Section of the Nasal Fossjs seen from behind 



(Arnold), f 



1, part of the frontal bone ; 2, crista galli ; 3, perpendicular plate of the ethmoid ; 

 between 4 and 4, the ethmoid cells ; o, right middle spongy bone ; 6, left lower spongy 

 bone ; 7, vomer ; 8, malar bone ; 9, maxillary sinus ; 10, its opening into the middle 

 meatus. 



In the individual parts of the nasal fossae the following particulars are to be 

 noticed. 



In the upper meatus, the small orifice which leads into the posterior ethmoidal 

 cells is lined by a prolongation of the thin mucous membrane which continues 



