340 



THE DIGESTIVE SYSTEM 



squamous variety. Upon the under surface and margins of the organ 

 its surface is smooth, but on the dorsum of the tongue the stratified 

 epithelium forms tall projections, which correspond with the papilla? 

 of the corium, and which constitute the so-called lingual papillae. These 

 papilla? are of three varieties: (1) conical or filiform; (2) fungiform; 

 and (3) circumvallate. 



The Conical or Filiform Papilla. These papilla? consist of flattened 



FIG. 320. FILIFORM 



ILL*: OP THE DOG'S TONGUE. 



a, papillae; b, corium; c, insertion of the muscular fibers into the border of the corium. 

 Hematein and eosin. Photo. X 60. 



and elongated epithelial cells which are often so arranged as to produce 

 a slender conical projection or epithelial tuft of variable height, which 

 covers the apex of each connective tissue papilla. This type is the 

 most abundant of the three varieties of lingual papilla?. They are 

 found upon all portions of the dorsum of the tongue. They range in 

 height from 0.5 to 2.5 millimeters. 



The Fungiform Papilla. The fungiform papilla? are formed by a 

 large connective tissue papilla or core which projects above the general 

 level of the epithelial surface and is covered by a smooth layer of strati- 

 fied squamous epithelium in which occasional taste buds are found. This 



