436 HEAD AND NECK 



where it disappears under cover of the hyo-glossus muscle. 

 There it divides into two branches. The smaller of these 

 extends anteriorly, upon the side of the tongue, and may be 

 traced as far as a point midway between the root and the tip. 

 The larger branch turns upwards, and is distributed to the 

 mucous membrane which invests the posterior third of the 

 dorsum linguae. It gives twigs to the vallate papillae, and 

 some fine filaments may be followed to the anterior surface 

 of the epiglottis. The glosso-pharyngeal nerve is a nerve of 

 taste and of common sensibility. 



The lingual and hypoglossal nerves are described on pages 

 289 and 316, and their terminal branches should now be 

 traced as far as is possible. 



Superior longi- 

 tudinal muscle 



Stylo-glossus' 



Inferior longi 

 tudinal muscle 



Hyo-glossus 

 Genio-glossus 



Hyoid bone Genio-hyoid 

 FlG. 173. Transverse section through the Tongue. (From Aeby. ) 



The internal laryngeal nerve gives a few delicate filaments 

 to the glosso-epiglottic and pharyngo-epiglottic folds and the 

 mucous membrane of the root of the tongue. 



The arteria profunda lingua should be followed to the tip 

 of the tongue, where it forms a small loop of anastomosis with 

 its fellow of the opposite side. 



Septum Linguae. The septum of the tongue can be seen 

 best by making a transverse section through the organ. This 

 will display, in a measure, the transverse and vertical muscular 

 fibres also. The septum is a median fibrous partition. It 

 is strongest posteriorly, where it is attached to the hyoid 

 bone. It does not reach the dorsum of the tongue, being 

 separated from it by the superior longitudinal muscle. 



