1050 



SPECIAL SENSE ORGANS 



section on the Respiratory System — and hence it is not necessary to describe 

 the whole nasal cavity. 



The olfactory area of the nose includes the uppermost part of the nasal fossae 

 on the lateral wall above the superior concha, and a slightly larger area of the 

 septum. 



Fig. 792 shows the size of this area, and it will be noticed that the area on the 

 lateral wall of the nose does not coincide with the area of the superior concha, but 

 is rather smaller. It should be added that the olfactory nerves can be traced 

 to a somewhat larger area of the mucous membrane, to the middle concha; 

 it is, therefore, possible that the area indicated is too small. 



The mucous membrane in the olfactory area has special characters, both naked 

 eye and microscopic, which distinguish it from the rest of the nasal mucous 



Fig. 792. — Diagram of the Distribution of the Nerves in the Nasal Cavity. (Poirier 

 and Charpy.) The olfactory area is represented by dots. A, septum. B, lateral wall. 



Posterior su 



f-\- / \ 'W V*"'"""'" ' Ant pal Posterior 



. -,-..> 'y // . \\ r> \ inferior nasal 



Anterior 

 palatine 



Posterior superior nasal 



membrane. It is usually of a yellowish colour, and is soft and pulpy in consistence 

 It is covered by a columnar ciliated epithelium and contains numerous glands 

 (glands of Bowman) . 



The olfactorj^ apparatus within it consists of the olfactory cells. These cells are elongated 

 spindle-shaped structures, lying between the deeper parts of the investing columnar cells. 

 From each a slender process passes to the surface of the mucosa, and terminates in a group of 

 short hair-like processes, the olfactory hairs (v. Bumm), while from the deep portion of the cell 

 a long slender process passes deeply into the mucosa. These processes resemble nerve filaments, 

 with no medullary sheath, and they pass in the olfactory nerves to the olfactory bulb, in which 

 they terminate in arborisation around the dendritic enlargements of the mitral cells of the 

 olfactory bulb (see fig. 795; also Olfactory Nerve, p. 929). 



Fig. 793. — Section Showing the Development of the Olfactory Pit. 



Olfactory 

 pit 



The connections of the olfactory bundle and tract with the brain are fully 

 dealt with in the section on the Nervous System. 



The development of the olfactory organ is connected with the development of the nose, 

 wliich represents at first only the (olfactory portion. About the third week, a localised thicken- 

 ing of tlie surface epithelium occiwrs on the antcro-ventral aspect of tlie head in the region of the 

 fore-brain, forming on each side an olfactory plate. 'J'hese plates In-come dej)ressod from the sur- 

 face by the growth of the margins, giving rise to the olfactory pits. The further changes are 



