THE DIGESTIVE SYSTEM 229 



(i) Vertical and somewhat radiating libres — hyoglossus, genio- 

 glossus, and vertical fibres of the lingiiaUs. 



(2) Transverse fibres — transverse fibres of the HnguaHs. 



(3) Longitudinal fibres — the styloglossus and longitudinal (supe- 

 rior and inferior) fibres of the lingualis. 



The connective tissue which supports the muscle fibres and sepa- 

 rates them into bundles contains mucous glands and fat. A strong 

 band of connective tissue, the septum linguce, extends lengthwise 

 through the middle of the tongue, dividing it into right and left halves. 



The suhmucosa of the tongue is not well developed, the stroma of 

 the mucosa resting directly upon the underlying muscle. 



-^ 



I'; 



ft 



~*K, 





h 



i^ - ■ 



rv - 



,Sa 



i»ej:.„ 



Fig. 134. — Vertical Section through Two Fihform Papillae from Human Tongue. 

 XSo. (Szymonowicz.) a, Horny epithelium; b, stroma; c, epithehum; d, secondary 

 papilla. 



The mucous membrane of the tongue resembles that of the mouth, 

 but differs from the latter in that in addition to the low papillae, 

 such as are found in the oral mucosa, the upper surface of the tongue 

 is studded with numerous and much larger papillae or villi. These 

 project from the surface -^^H p^ive to the tongue its characteristic 

 roughness. Three form: are distinguished: — Fihform, 



fungiform, and circumva 



