26 SPECIAL SENSES. 



brane. This membrane is closely adherent to the fibrous cov- 

 erings of the bones and cartilages by which the nasal fossae 

 are bounded, and is thickest over the turbinated bones. It is 

 continuous with the membrane lining the pharynx, the nasal 

 duct and lachrymal canals, the Eustachian tube, the frontal, 

 ethmoidal, and sphenoidal sinuses, and the antrurn. There 

 are openings leading from the nasal fossae to all of these 

 cavities. 



The essential organ of olfaction is the mucous membrane 

 lining the upper half of the nasal fossae. Not only has it 

 been shown anatomically that this part only of the membrane 

 receives the terminal filaments of the olfactory nerves, but 

 physiological experiments have demonstrated that it is the 

 only part capable of receiving odorous impressions. If a tube 

 be introduced into the nostril, placed horizontally over an 

 odorous substance so that the emanations cannot penetrate its 

 caliber, no odor is perceived, though the parts below the end 

 of the tube might receive the emanations ; but, if the tube be 

 now directed toward the odorous substance, so that the ema- 

 nations can penetrate to the upper portion of the nares, the 

 odor is immediately appreciated. 1 



That portion of the lining of the nasal fossae properly 

 called the olfactory membrane extends from the cribriform 

 plate of the ethmoid bone downward a little less than an inch. 

 It is exceedingly soft and friable, very vascular, thicker than 

 the rest of the Schiieiderian membrane, and, in man, has 

 rather a yellowish color. It is covered by long, delicate, co- 

 lumnar cells, nucleated, each one provided with from three 

 to eight ciliary processes, their movement being from before 

 backward. 2 The existence of cilia in this situation has been 

 denied by some observers. 9 The mucous glands of the olfac- 

 tory membrane are numerous, long, and racemose. 4 They 



1 LONGET, Traite de physiologic, Paris, 1869, tome iii., p. 45. 



2 SAPPEY, Traite d* anatomic, Paris, 1871, tome iii., p. 654. 



3 KOLLIKER, Handbuch der Gewebelehre, Leipzig, 1867, S. 741. 



4 SAPPEY, loc. cit. 



