816 



THE ORGANS OF SPECIAL SENSE. 



on the Hyo-glossus muscle in the submaxillary region, and thence to the deep 

 glands of the neck. 



The nerves of the tongue are five in number in each half: the lingual branch 

 of the fifth, which is distributed to the papillae at the fore part and sides of 

 the tongue, and forms the nerve of ordinary sensibility for its anterior two-thirds ; 

 the chorda tympani, which runs in the sheath of the lingual, is generally regarded as 



Glosso-pharyn- 

 geal nerve. 



Superior laryn- 

 geal nerve. 



FIG. 433. Under surface of tongue, showing the distribution of nerves to this organ. (From a preparation 

 in the Museum of the Royal College of Surgeons of England.) 



the nerve of taste for the same area ; the lingual branch of the glosso-pharyngeal, 

 which is distributed to the mucous membrane at the base and sides of the tongue, 

 and to the papillae circumvallatee, and which supplies both sensory and gustatory 

 filaments to this region ; the hypo-glossal nerve, which is the motor nerve to the 

 muscular substance of the tongue ; and the superior laryngeal, which sends some 

 fine branches to the root near to the epiglottis. Sympathetic filaments also pass 

 to the tongue from the nervi molles on the lingual and other arteries supplying it. 



Surgical Anatomy. The diseases to which the tongue is liable are numerous, and its 

 surgical anatomy of importance, since any or all the structures of which it is composed muscles, 

 connective tissue, mucous membrane, glands, vessels, nerves, and lymphatics may be the seat 

 of morbid changes. It is not often the seat of congenital defects, though a few cases of vertical 

 cleft have been recorded, and it is occasionally, though much more rarely than is commonly sup- 

 posed, the seat of "tongue-tie," from shortness of the frasnum. (See page 489.) 



There is, however, one condition which must be regarded as congenital, though it does not 

 sometimes evidence itself until a year or two after birth, which is not uncommon. This is an 

 enlargement of the tongue which is due primarily to a dilatation of the lymph-channels and a 

 greatly increased development of the lymphatic tissue throughout the tongue. This is often 



