DISTKIBUTION OF FIBERS AND END ORGANS 445 



the tongue. If the tongue is protruded and its surface 

 examined with the aid of a mirror it is possible to dis- 



Fig. 207 — The tongue; K, filiform papillEe; /, fungiform papillje; L, circumval- 



late papillae. 



tinguish many raised points on the surface of its mucous 

 membrane. These raised points are called papillse, and are 

 of three forms — the circumvallate, fungiform, and filiform. 

 Of these, the circumvallate are the largest and least numer- 

 ous. They appear as circular extensions of the membrane 

 and are surrounded by a little depression or ditch. They 

 are only seven to twelve in number, and lie on the upper 

 surface near the root of the tongue. 



