266 



THE DIGESTIVE SYSTEM 



invests the rounded blunt extremity of the muscle cell. Many of 

 these muscle fibres are branched. 



The mucous membrane of the tongue consists of a thick corium, 

 and an epithelial covering. The deeper part of the corium, con- 

 sisting of loose areolar tissue, is intimately connected with the 



FIG. 223. ONE LATERAL HALF OK A CORONAL SECTION OF A DOG'S TONGUE. 



The dorsal surface presents numerous large filiform papillae, a, lingual papillae ; 6, corium ; 



c, the fibro-muscular substance of the tongue. Hematein and eosin. Photo, x 6. 



muscle. The superficial portion of the corium, containing denser 

 areolar tissue, carries upon its surface papillce of unusually large 

 size which project into the epithelial coat. The surface of the 

 larger of these papillae is not smooth, but is covered with small 

 secondary papillce. 



The epithelium of the tongue is of the stratified 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 papillae of the corium, 

 and which constitute the so-called lingual papillce. These papillae 

 are of three varieties : 1, conical or filiform ; 2, f ungif orm ; and 3, 

 circumvallate. 



