158 



SENSE OF SMELL. 



58 - 



has to make the impression. The 

 membrane lines the whole of the 

 bony cavities called nasal fossse, 

 which are constantly open anteriorly 

 and posteriorly, to permit the air 

 that traverses them to proceed to the 

 lungs. The anterior aperture is 

 covered by a kind of pent-house or 

 capital, for the purpose of collecting 

 the odorous particles. This capital 

 is called the nose. The essential 

 part of the organ is the pituitary or 

 olfactory membrane, the other 

 parts being superadded to perfect the 

 sense. 



The bony portions of the nose are 

 separated from each other by the 

 vomer. This bony septum is pro- 

 longed, by means of cartilage, to 

 the anterior extremity of the nose, 



Qn fV, n f- fh A Yiasal fn;<3fp irp 

 > tnat tft6 nasal 



Vertical Section of the Middle Part of the 

 Nasal Fossae, giving a Posterior View of 

 the Arrangement of the Ethmoidal Cells, 

 &c. 



1. Anterior fossae of the cranium. 2. The 

 same covered by the dura mater. 3. Dura mater 

 turned up. 4. Crista galli of the ethmoid bone. 

 5. Its cribriform plate. 6. Its nasal lamella. 

 7. Middle spongy bones. 8. Ethmoidal cells. 

 9. Os planum. 10. Inferior spongy bones. 11. 

 Vomer. 12. Superior maxillary bone. 13. Its 



union with the ethmoid. 14. Anterior parietes into like parts, which haVC no 

 of the antrum Highmorianum, covered by its . r . , ' , , 



membrane. 15. Its fibrous layer. 16. Its mucous niCatlOn With each Other, but Open 

 membrane. 17. Palatine process of the superior j. ,1 , i , j.'L- j. 



maxillary bone. 18. Roof of the mouth, cov- together, posteriorly, into the top 

 ered by the mucous membrane. 19. Section of n f fVi/i -nil Ji rvn Y \VithiTi papli nf 



this membrane. A bristle in the orifice of the Ot ttl6 P nar J nx - W 1WL 



antrum Highmorianum. the nares are two convoluted or 



turbinated bones generally called 



ossa spongiosa vel turlinata; and, by the French, cornets. These 

 are situate one above the other ; the superior formed of a plate of the 

 ethmoid' bone the inferior a distinct bone. They divide the general 

 cavity of each nostril into three passages or meatus. The inferior 

 meatus is broad and long ; the least oblique, and least tortuous ; the 

 middle is narrow, almost as long, but more extensive from above to 

 below ; and the superior is much shorter, more oblique, and still nar- 

 rower. The narrowness of these passages in the living subject is so 

 great, that the slightest tumefaction of the membrane renders the 

 passage of air through the fossae extremely difficult. This is the cause 

 of the difficulty of breathing through the nose, that attends " a cold 

 in the head." Into the two upper passages, cavities in certain bones 

 open, which considerably enlarge the extent of the fossae. These are 

 called sinuses; and are the maxillary, palatine, frontal, sphenoidal, 

 ethmoidal, the last being sometimes termed ethmoidal cells. 



All the cavities are lined by the delicate pituitary membrane, or by 

 a prolongation of it. In the nasal fossae it augments the thickness of 

 the turbinated bones. It resembles the mucous membranes in general 

 in its composition ; and adheres firmly to the bones and cartilages, 

 which it covers. Its aspect is velvety, owing to a multitude of minute 

 papillae ; and it receives a great number of vessels and nerves. The 

 sinuses are lined by a prolongation apparently of the same membrane, 

 differing, however, in some respects from the other. The whole of the 



