TASTE. 483 



va llate pa-pill se. These are the rounded eminences which form the 

 V-shaped figure near the situation of the foramen caecum. They 

 are eight or ten in number. Each one of them is surrounded by 

 a circular wall, or circumvallation, of mucous membrane, which 

 gives to them their distinguishing appellation. The circumvalla- 

 tion, as well as the central eminence, has a structure similar to that 

 of the fimgiform papillae. 



The sensitive nerves of the tongue, as we have already seen, are 

 two in number, viz., the lingual branch of the fifth pair, and the 

 lingual portion of the glosso-pharyngeal. The lingual branch of 

 the fifth pair enters the tongue at the anterior border of the hyo- 

 glossus muscle, and its fibres then run through the muscular tissue 

 of the organ, from below upward and from behind forward, with- 

 out any ultimate distribution, until they reach the mucous mem- 

 brane. The nervous filaments then penetrate into the lingual 

 papillae, where they finally terminate. The exact mode of their 

 termination is not positively known. According to Kolliker, they 

 sometimes seem to end in loops, and sometimes by free extremities. 



The lingual portion of the glosso-pharyngeal nerve passes into 

 the tongue below the posterior border of the hyo-glossus muscle. 

 It then divides into various branches, which pass through the mus- 

 cular tissue, and are finally distributed to the mucous membrane of 

 the base and sides of the organ. 



Fig. 153. 



DIAGRAM OF To NOUE, with its sensitive nerves and papillae. 1. Lingual branch of fifth pair, 

 2. Glosso-pharyngeal nerve. 



The mucous membrane of the base of the tongue, of its edges, 

 and its under surface near the tip, as well as the mucous membrane 

 of the mouth and fauces generally, is also supplied with mucous 

 follicles, which furnish a viscid secretion by which the free surface 

 of the parts is lubricated. 



