THE CRANIAL OR ENCEPHALIC NERVES. 821 



"Wharton's duct — to enter the space separating the genio-glossus from the hyo- 

 glossus longus and brevis muscles. From this point it continues to near the free 

 extremity of the tongue, proceeding in a veiy flexuous manner, and giving off, 

 on its course, divisions equally tortuous, which traverse the organ, but without 

 detaching any ramuscules to the lingual muscles ; these divisions terminate in 

 the middle and anterior portions of the lingual mucous membrane. 



Before penetrating the mass of the tongue, this nerve furnishes : 1. At, and 

 in front of, the posterior pillars of that organ, some small ramuscules which are 

 sometimes plexiform, and are distributed to the mucous membrane at the base of 

 the tongue. 2. Lower, and behind, one or two thin filaments which are carried 

 to Wharton's duct, and ascend with it to the maxillary gland. 3. A sublingual 

 branch, the divisions of which enter the gland of that name, as well as the 

 mucous membrane covering the sides of the tongue. 



The gustatory nerve receives, near its origin, the tympano-lingual filament or 

 chorda tympani — a branch of the facial nerve soon to be described. Its terminal 

 divisions mix and anastomose with those of the great hypoglossal nerve, in the 

 deep muscular interstice which lodges both. 



Physiology teaches us that the gustatoiy nerve gives to the anterior two-thirds 

 of the lingual mucous membrane ordinary sensation, and, in addition, that 

 special sensibility (or gustatory power) by virtue of which that membrane enjoys 

 the property of appreciating savours. This is its exclusive function. With 

 regard to the tympanic filament from the facial nerve, and which is joined to the 

 gustatory, Bernard is of opinion that it participates in the exercise of this sense 

 of taste. Its radiating fibres extend to the submucous muscular layer of which 

 we have spoken, and on which the lingual papillse rest, and endow it with the 

 property of acting on these papillse by adapting them, we may say, to the sapid 

 substances brought into contact with them. Lussana goes further than this, 

 and, basing his statement on observations made on Man and on experiments, 

 asserts that the nerve of the tympanum passes to the mucous membrane, and 

 endows it with the sense of taste. It may be added that Yulpian did not at one 

 time agree to either of these opinions, because, according to his experience, this 

 nerve did not go to the tongue, but stopped at the submaxillary ganglion ; now, 

 however, he admits that some of its fibres pass into the lingualis muscle, and may 

 aid in causing movement of the tongue. Prevost, of Geneva, believes that the 

 chorda tympani joins the internal branch of the Ungual nerve. 



6. Mylo-hyoidean Nerve (Fig. 453, 13). — The designation of this nerve 

 indicates its destination and uses. It goes to the muscle bearing its name, and 

 excites its contractility ; it arises opposite to the preceding, and, like it, descends 

 between the internal pterygoid muscle and the inferior maxillary bone, adhering 

 somewhat closely to the latter. But arriving at the posterior border of the mylo- 

 hyoideus muscle, it passes to the outside of it, and, meeting the sublingual 

 artery, ramifies with it on the external face of that muscle. 



7. Dental Branches (Fig. 453, 12). — These are of two orders : some 

 passing to the molar, the others to the canine and incisor teeth. Their description 

 does not merit any special indication. 



8. Mental Nerves, or Terminal Branches of the Inferior Maxillary 

 Nerve. — Perfectly analogous to the infra-orbital ramuscules, these nerves form 

 a fasciculus by diverging and flexuous branches, which leave the mental foramen 

 to be distributed to the textures of the lower lip, after receiving a branch from 

 the facial nerve (Fig. 453, 11'). 



