THE TONGUE 



1223 



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 gen- 

 erally regarded as the nerve of taste for the same area (p. 1000); the lingual branch of theglosso- 

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

 and to the papillae circumvallatae, and which supplies both sensor and gustatory filaments to 

 this region; the hypoglossal nerve, which is the motor nerve to the muscular substance of the 

 tongue; and the internal laryngeal branch of 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 molleft on the lingual a ad other arteries supplying it. Some of the nerves end free 

 between the cells of epithelium; others terminate as end organs (Meissner's corpuscles and 

 the end-bulbs of Krause), and in taste buds as sensor dendrites (p. 1151). 



Glosso-nharyn- 

 geal nerve. 



FIG. 943.- 



Internal laryncienl . 

 branch of the / 

 superior laryngeal 

 nerve. 



-Under surface of tongue, showing the distribution of nerves to this organ, 

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



(From a preparation 



The Development of the Tongue (Figs. 944 and 945). The tongue is developed in the floor 

 of the pharynx. The rudiment of the anterior or buccal portion appears during the third week 

 as a rounded elevation, immediately behind the ventral ends of the mandibular arches. This 

 elevation is named the tuberculum impar (Figs. 944 and 945); it extends forward on the oral 

 surface of the mandibular arch, and increases markedly in size by the development of a pair of 

 lateral tongue elevations, which raise themselves from the inner surfaces of the mandibular 

 arches, and, blending with the tuberculum impar, form the tip and greater portion of the buccal 

 part of the tongue. These lateral growths correspond with similar structures which were de- 

 scribed by E. Kallius in the development of the tongue of the lizard. From the ventral ends of the 

 fourth arch there arises a second and larger elevation, in the centre of which is a median groove 

 or furrow. This elevation is named the furcula (Fig. 944), and is at first separated from the 

 tuberculum impar by a depression, but later by a ridge formed by the forward growth and fusion 

 of the ventral ends of the second and third arches. The posterior or pharyngeal part of the 

 tongue is developed from this ridge, which extends forward in the form of a V, so as to embrace 

 between its two limbs the tuberculum impar (Figs. 944 and 945). At the apex of the V a pit- 



