THE SENSE OF SMELL. 



74;] 



are, for the most part, confined to this latter region. The mucous 

 membrane which covers this portion of the nasal cavity is, in struc- 

 ture and appearance, very similar to that of the trachea. It is com- 

 posed of layers of ciliated epithelium which rest upon a basement 

 membrane rich in blood-vessels and lymphatics. Among the ciliated 

 cells are found numerous goblet and mucous cells, whose secretions 

 keep the surface of the mucous membrane soft and moist. In it are 

 numerous filaments of the trigeminus, which endow it with tactile 



1 



Fig. 304. (BISHOP.) 



1, Middle turbinated body turned aside and held by a hook. 2, Nasal duct 

 and valves. 3, Canal leading to the maxillary and frontal sinuses. 4, Inferior 

 turbinated body showing the location of the mouth of the nasal duct in the 

 cul-de-sac. 



sensibility. There are no filaments of the olfactory nerve in this 

 region. 



The olfactory mucous membrane is thicker than that of the 

 respiratory portion. To the naked eye it presents a yellow or brown- 

 yellow color because of the pigment contained within it. By reason 

 of its color it is very readily distinguished from that of the Schneider- 

 ian membrane. Its surface is covered by a single layer of cylindrical 

 epithelium whose cells are often branched at their lower ends. 



