992 ORGANS OF THE SENSES AND THE COMMON INTEGUMENT 



nucleus near the middle of the cell. The peripheral end of the cell terminates at the gustatory 

 pore in a fine hair-like filament, the gustatory hair. The central process passes toward the deep 

 extremity of the bud, and there ends in single or bifurcated varicosities. The nerve fibrils after 

 losing their medullary sheaths enter the taste bud, and end in fine extremities between the gusta- 

 tory cells; other nerve fibrils ramify between the supporting cells and terminate in fine extremities; 

 these, however, are believed to be nerves of ordinary sensation and not gustatory. 



Gustatory pore and 

 gustatory hairs 



FIG. 851. Taste-bud, highly magnified. 



Nerves of Taste. -The chorda tympani nerve, derived from the sensory root of the facial, is 

 the nerve of taste for the anterior two-thirds of the tongue; the nerve for the posterior third 

 is the glossopharyngeal. 



THE ORGAN OF SMELL (ORGANON OLFACTORIUS; THE NOSE). 



The peripheral olfactory organ or organ of smell consists of two parts : an outer, 

 the external nose, which projects from the center of the face; and an internal, the 

 nasal cavity, which is divided by a septum into right and left nasal chambers. 



The External Nose (Nasus Externus; Outer Nose). 



The external nose is pyramidal in form, and its upper angle or root is connected 

 directly with the forehead ; its free angle is termed the apex. Its base is perforated 

 by two elliptical orifices, the nares, separated from each other by an antero-posterior 

 septum, the columna. The margins of the nares are provided with a number of 

 stiff hairs, or vibrissse, which arrest the passage of foreign substances carried with 

 the current of air intended for respiration. The lateral surfaces of the nose form, 

 by their union in the middle line, the dorsum nasi, the direction of which varies 

 considerably in different individuals; the upper part of the dorsum is supported 

 by the nasal bones, and is named the bridge. The lateral surface ends below in 

 a rounded eminence, the ala nasi. 



Structure. The frame-work of the external nose is composed of bones and cartilages; it is 

 covered by the integument, and lined by mucous membrane. 



The bony frame-work occupies the upper part of the organ; it consists of the nasal bones, and 

 the frontal processes of the .maxillae. 



The cartilaginous frame-work (cartilagines nasi) consists of five large pieces, viz., the cartilage 

 of the septum, the two lateral and the two greater alar cartilages, and several smaller pieces, 

 the lesser alar cartilages (Figs. 852, 853, 854). The various cartilages are connected to each other 

 and to the bones by a tough fibrous membrane. 



The cartilage of the septum (cartilago septi nasi) is somewhat quadrilateral in form, thicker at 

 its margins than at its center, and completes the separation between the nasal cavities in front. 

 Its anterior margin, thickest above, is connected with the nasal bones, and is continuous with 

 the anterior margins of the lateral cartilages; below, it is connected to the medial crura of the 

 greater alar cartilages by fibrous tissue. Its posterior margin is connected with the perpendicular 

 plate of the ethmoid; its inferior margin with the vomer arid the palatine processes of the maxillae. 



