The next branches of the nerve are those which are given off by it while within the inferior maxillary canal : they have two desti nations, viz. the roots and periosteum of the teeth and the gum of the lower jaw. During its course through the canal the nerve gives off several long, slender branches, which run for some distance within the canal, ascend thence through the hone beneath and on either side of the roots of the teeth, ramify as they proceed, and distribute their ramifications to the desti nations which have been mentioned. The author has never found these branches as they are for the most part represented, viz. short single filaments ascending almost directly into the several fangs of the teeth : they are deci dedly less remarkable and less numerous in the old subject after the fall of the teeth than in the young. Again, at the mental foramen, and immediately before its escape from the canal, the nerve gives off a more considerable branch, denominated by Cruveilhier dentaire which is continued through the jaw toward the symphysis beneath the canine and incisor teeth, and distributed to them. The former set supplies the posterior molar teeth. Accord ing to the general opinion the nerves of the teeth enter the fangs through the apertures in their extremities, and are transmitted through them into the bodies of the teeth, to be con sumed in the pulp and the structure of the teeth themselves, 1. Ilunter, however, has stated in his work on the teeth, that lie has never succeeded in tracing nerves into the fangs, and the experience of the writer, so 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 rectal calf tney 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 minus 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. !laving 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 myluhyoid, where it is situate betweeu the mucous membrane of the mouth and tho 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 liyoides, and the duet 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.