THE SENSE OF TASTE. 235 



lining the commencement of the alimentary canal, and is furnished 

 with vascular and nervous papillae. 



The papilla? are analogous in their structure to those of the skin, 

 and are distributed over the dorsum of the tongue, giving it its char- 

 acteristic roughness. 



There are three principal varieties 



1. The filiform papilla are most numerous, and cover the anterior two 

 thirds of the tongue ; they are conic or filiform in shape, often 

 prolonged into filamentous tufts, of a whitish color, and covered 

 by horny epithelium. 



2. The fungi form papilla are found chiefly at the tip and sides of 

 the tongue ; they are larger than the preceding, and may be recog- 

 nized by their deep red color. 



3. The circumvallate papilla are rounded eminences from eight to 

 ten in number, situated at the base of the tongue, where they 

 form a V-shaped figure. They are quite large, and consist of a 

 central projection of mucous membrane, surrounded by a wall, 

 or circumvallation, from which they derive their name. 



The taste-beakers, supposed to be the true organs of taste, are 

 flask-like bodies, ovoid in form, about ^ - of an inch in length, 

 situated in the epithelial covering of the mucous membrane, on the 

 circumvallate papillae. They consist of a number of fusiform, narrow 

 cells, which are curved so as to form the walls of this flask-like body ; 

 in the interior are elongated cells, with large, clear nuclei, the 

 taste-cells. 



Nerves of Taste. The chorda tympani nerve, a branch of the 

 facial, after leaving the cavity of the tympanum, joins the third 

 division of the fifth nerve between the two pterygoid muscles, and 

 then passes forward in the lingual branches, to be distributed to the 

 mucous membrane of the anterior two thirds of the tongue. Division 

 or disease of this nerve is followed by a loss of taste in the part to 

 which it is distributed. 



The glossopharyngeal enters the tongue at the posterior border of 

 the hyoglossus muscle, and is distributed to the mucous membrane of 

 the base and sides of the tongue, fauces, etc. 



The lingual branch of the trifacial nerve endows the tongue with 

 general sensibility ; the hypoglossal endows it with motion. 



