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Elementary Biology. 



FIG. 17*?. SENSORY EPITHELIUM FROM 

 THE NOSE. (Schafer.) 



by a groove or ditch : hence the name of circumvallate 

 applied to these papillae. On the sides of this groove are 

 situated numerous flask-shaped depressions, formed of long 

 stave-like epithelial cells, whose outer ends project freely 

 into the vallum, while their inner ends are in communica- 

 tion with the axis cylinder of the glosso-pharyngeal nerve. 



Soluble substances introduced 

 into the groove must of ne- 

 cessity stimulate the nerve- 

 terminations through the epi- 

 thelial cells. 



Smell. The sense of 

 smell is located in the rose. 

 The interior of the nasal 

 capsule is ridged in such a 

 manner as to largely increase 

 the surface .of the chamber- 

 wall. The terminations of 

 the nerves of smell are dis- 

 tributed over the mucous 

 membrane covering the 

 ridges, and their axis-cylin- 

 ders end in long spindle- 

 shaped cells, whose pointed 

 free ends project from the 

 surface of the membrane. 

 Air bearing odoriferous par- 

 ticles enters the anterior 

 nares and stimulates the 

 nerve - terminations in its 

 passage over the ridges projecting from the walls of the 

 nasal capsule. 



Hearing. The organ of hearing is much more compli- 

 cated, though fundamentally the same in principle as the 

 sense-organs already described. Without entering into detail, 

 it will be sufficient to say that the auditory or periotic 



and 2, varieties of olfactory epithe- 

 lium and supporting cell-; 3, termi- 

 nation of the olfactory nerve. 



