940 



THE NERVOUS SYSTEM 



inner surface as far forward as the angle of the mouth. The fibres of the anterior deep temporal 

 nerve, a branch of the masticator, are frequently associated with the buccinator until the latter 

 has passed between the heads of the external pterygoid; then the anterior deep temporal nerve 

 separates from the buccinator and passes upward on the lateral surface of the upper head of the 

 external pterygoid. 



The posterior portion of the mandibular nerve divides into three large branches. 

 Two of these, the lingual and the auriculo-temporal nerves, are exclusively- 

 sensory; the third, the inferior alveolar (dental) nerve, contains a strand of motor 

 fibres, the mylo-hyoid nerve, which comprise a branch of the masticator nerve. 



The lingual nerve is the most anterior branch of the mandibular nerve (figs. 

 736, 743). It lies in front and to the medial side of the inferior alveolar (dental) 

 nerve and descends at first on the medial side of the pterygoideus externus, then 

 between the pterygoideus internus and the ramus of the mandible to the posterior 

 part of the mylohyoid ridge, where it passes off the anterior border of the ptery- 

 goideus internus; at this point it is situated a short distance behind the last 



Fig. 736.- 



-DlSTRIBtrTION OF THE MANDIBULAR DIVISION OF THE TRIGEMINUS COMBINED WITH 



Branches of the Masticator Nerve. (Henle.) 



Buccinator neive 



Anterior deep tem- 

 poral nerve 



Auriculo-temporal 



nerve 

 Posterior deep 

 temporal nerve 



Nerve to masseter 



Chorda tympani 



Mylo-hyoid nerve 



Lingual nerve 



Inferior alveolar 

 nerve 



molar tooth and is covered in front by the mucous membrane of the posterior 

 part of the mouth cavity. After leaving the pterygoideus internus it crosses the 

 fibres of the superior constrictor, which are attached to the mandible, and turns 

 forward toward the tip of the tongue, crossing the lateral surfaces of the stylo- 

 glossus, hyoglossus, and genioglossus. In its course across the hyoglossus it 

 lies first above, then to the lateral side of, and finally below Wharton's duct, and 

 as it ascends on the genioglossus it lies on the medial side of the duct. 



Communications and branches. — While it is on the medial side of the pterygoideus externus 

 the lingual nerve is joined, at an acute angle, by tlie chorda tympani (figs. 730, 743), a branch 

 of the glos.so-palatiii(! n(!rv(\ and as it lies b(>tw('on tlie rairuis of the m.'uidiblc and the pterygoid- 

 eus internus it is conncn-.ted by a brancli willi tlie inferior alveolar (dental) nerve, and gives off 

 one or two small branches, the rami isthmi faucium, whi(!h are ditrihuted as sensory fibres to 

 the tonsil and the mucous membrane of the i)osterior part of the mouth (fig. 743). 



Wiiile it is above the duct it gives a branch, whicli contains many sensory and visceral 

 motor chorda tympani fibres, to tlie sul)maxillary ganglion (.soej). 963), and it receives branches, 

 chiefly sympathetic, from that ganglion. A little lurthcr forward it is connected by one or two 

 branches, which run along the anterior border of the hyoglossus, with the hypoglossal nerve 



