FIFTH PAIR OF NERVES. 



295 



teeth themselves. J. Hunter, however, has 

 stated in his work on the teeth, that he has 

 never succeeded in tracing nerves into the fangs, 

 and the experience of the writer, sa far as it 

 extends, tends to confirm the doubt thus ex- 

 pressed; he has frequently traced the filaments 

 to the structure at the root of the fang, but 

 never into the fang, and in the jaw of the foetal 

 calf they may be found distributed in number 

 upon the membrane of the pulp, but he has 

 not been able to follow them into the pulp 

 itself. 



The filaments sent into the gums from the 

 dental nerves, superior as well as inferior, 

 traverse the alveolar arch, escape from the bone 

 upon its gingival aspect, and at once enter the 

 gum : they are well represented by Arnold. 



The final branches of the inferior maxillary 

 nerve are the inferior labial, internal and exter- 

 nal. Of these the internal is the larger; it 

 ascends toward the mouth, inclining inward, 

 and breaks up into a great number of ramifica- 

 tions, which are distributed to the depressor 

 labii inferioris, the depressor anguli oris, the 

 orbicularis, and the levator menti, also to the 

 integument and internal membrane of the lip, 

 and to the labial glands; they anastomose with 

 branches of the inferior division of the portio 

 dura. The external inclines toward the angle 

 of the mouth ; it also gives off a great number 

 of ramifications, distributed to the depressor 

 anguli, the orbicularis, and the insertion of the 

 muscles at the angle, the integument, and 

 internal membrane of the lip, and the labial 

 glands; it also anastomoses with branches of 

 the portio dura. 



The lingual branch of the third division. 

 The situation and relative size and position of 

 the lingual and inferior maxillary branches in 

 the first part of their course, have been already 

 described. Having crossed the internal maxil- 

 lary artery, the lingual branch pursues its course 

 downward, forward, and inward, passing first 

 between the pterygoid muscles in the manner 

 described, and then between the internal ptery- 

 goid and the ramus of the jaw, until it has 

 reached the anterior margin of that muscle; 

 during this part of its course it is at first 

 separated from the inferior maxillary nerve by 

 the internal lateral ligament, which is placed 

 between them, the lingual branch internal, the 

 maxillary external to it, and afterward it is 

 situate anterior and superior to the mylohyoid 

 branch of the maxillary. Having reached the 

 margin of the pterygoid it emerges from between 

 the muscle and the jaw, immediately behind 

 the posterior extremity of the mylohyoid ridge, 

 and enters into the digastric or submaxillary 

 space, in which it is among the parts most 

 deeply situate; within this space it continues to 

 run forward and inward, until, at the anterior 

 extremity, it attaches itself to the under surface 

 of the tongue, and is prolonged by one of its 

 branches to the extremity of that organ. During 

 its course through the digastric space, it is at 

 first left uncovered by the muscles inferiorly, 

 and in the interval between the margin of the 

 pterygoid and that of the mylohyoid, where it 

 is situate between the mucous membrane of 



the mouth and the posterior extremity of the 

 submaxillary gland ; it then passes internal to 

 the mylohyoid muscle, between it and the 

 stylo-glossus, hyo-glossus, and genio-glossus, 

 and is at the same time contained in a triangu- 

 lar or wedge-shaped space, the base of which 

 is above and the apex below; this space is 

 bounded above by the mucous membrane of 

 the mouth, externally by the mylohyoid muscle, 

 and internally by the hyo-glossus, stylo-glossus, 

 and genio-glossus muscles. In it are contained 

 the sublingual gland, the deep process of the 

 submaxillary and the duct of that gland with 

 the lingual branch of the fifth and the ninth 

 nerves; in the anterior part and superiorly, 

 immediately beneath the mucous membrane, 

 is situate the sublingual gland ; at the posterior 

 and rather inferiorly the deep process of the 

 submaxillary; while the nerves and the duct 

 are placed at the posterior or external part of 

 the lingual branch of the fifth above, imme- 

 diately beneath the mucous membrane ; the 

 ninth below, along, and above the cornu of 

 the os hyoides, and the duct between the 

 nerves; but as the three parts pass forward, 

 the duct and lingual branch cross each other, 

 the nerve descending, the duct ascending be- 

 tween the nerve and the hyo-glossus, and in 

 consequence of this circumstance, at the ante- 

 rior part of the space, the duct is superior, the 

 lingual branch is intermediate, and the ninth 

 nerve is below. At first the lingual branch is 

 above the deep process of the submaxillary 

 gland, then it is situate internal and superior to 

 it, external and inferior to the duct ; as it pro- 

 ceeds, it is beneath the sublingual gland, and, 

 lastly, it ascends internal to that gland, between 

 it and the genio-glossus, in order to reach the 

 tongue. 



At the posterior part of the space, the nerve 

 is immediately beneath the mucous membrane ; 

 as it proceeds it descends from, but toward 

 the anterior part again ascends, and is in con- 

 tact with the membrane as it becomes attached 

 to the tongue. 



Having reached the anterior margin of the 

 hyo-glossus the nerve breaks up into three 

 branches, posterior, middle, and anterior. Of 

 these the posterior is the shortest, and ascends 

 almost directly; the middle runs upward and 

 forward, and the anterior, which is much 

 longer than, and at the same time inferior to 

 the others, almost directly forward, along the 

 under surface of the tongue, between the genio- 

 glossus and the stylo-glossus; the former 

 muscle internal, the latter external -to it. In 

 its course beneath the tongue it is accompanied 

 by the ranine artery, which joins it at the 

 anterior margin of the hyo-glossus, and is 

 situate inferior to it, immediately above the 

 mucous membrane. 



The lingual nerve does not give off many 

 branches in the first part of its course : soon 

 after its origin it receives the branch of com- 

 munication, by which the inferior dental nerve 

 is connected to it. About the same point or 

 presently after it is also joined by the chorda 

 tympani. The uncertainty which has prevailed 

 with regard to the source of this nerve renders 



