THE BRANCHES OF THE FIFTH NERVE. 



737 



tube ; the latter arises from the ganglion, near the origin of the internal pterygoid 

 nerve, and passes forward. The fibres of these nerves are, however, mainly derived 



FIG. 397. The otic ganglion and its branches. 



from the nerve to the Internal pterygoid muscle. It also gives off a small com- 

 municating branch to the chorda tympani. 



The Submaxillary Ganglion (Fig. 395). 



The submaxillary ganglion is of small size, fusiform in shape, and situated 

 above the deep portion of the submaxillary gland, near the posterior border of the 

 Mylo-hyoid muscle, being connected by filaments with the lower border of the 

 lingual (gustatory) nerve. 



Branches of Communication. This ganglion is connected with the lingual 

 (gustatory) nerve by a few filaments which join it separately at its fore and back 

 part. It also receives a branch from the chorda tympani, by which it communicates 

 with the facial, and communicates with the sympathetic by filaments from the 

 sympathetic plexus around the facial artery. 



Branches of Distribution. These are five or six in number: they arise from 

 the lower part of the ganglion, and supply the mucous membrane of the mouth and 

 Wharton's duct, some being lost in the submaxillary gland. The branch of com- 

 munication from the lingual to the fore part of the ganglion is by some regarded 

 as a branch of distribution, by which filaments of the chorda tympani pass from 

 the ganglion to the nerve, and by it are conveyed to the sublingual gland and the 

 tongue. 



Surface Marking. It will be seen from the above description that the three terminal 

 branches of the three divisions of the fifth nerve emerge from foramina in the bones of the skull 

 and face on to the face : the terminal branch of the first division emerging through the supra- 

 orbital foramen ; that of the second through the infra-orbital foramen ; and the third through 

 the .mental foramen. The supra-orbital foramen is situated at the junction of the internal 

 and middle third of the supra-orbital arch. If a straight line is drawn from this point to the 

 lower border of the inferior maxillary bone, so that it passes between the two bicuspid teeth of 

 the lower jaw, it will pass over the infra-orbital and mental foramina, the former being situated 

 about one centimetre (two-fifths of an inch) below the margin of the orbit, and the latter varying 

 in position according to the age of the individual. In the adult it is midway between the upper 

 and lower borders of the inferior maxillary bone ; in the child it is nearer the lower border ; and 

 in the edentulous jaw of old age it is close to the upper margin. 

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