I2IO A MANUAL OF ANATOMY 



descends upon the spheno-mandibular ligament and internal 

 pterygoid muscle to the inferior dental foramen, through which it 

 passes into the inferior dental canal, after having parted with its 

 mylo-hyoid branch. The lingual nerve is anterior and internal 

 to it, and the inferior dental artery is posterior and external to it. 

 Within the dental canal the nerve is accompanied by the inferior 

 dental artery, and, having arrived at the level of the mental foramen, 

 it terminates by dividing into two branches, mental and incisor. 



Branches. — (i) The mylo-hyoid nerve is given off from the parent 

 trunk just before it passes through the inferior dental foramen. It 

 conducts away all the motor fibres from the parent trunk, and in 

 company with the mylo-hyoid artery pierces the lower part of 

 the spheno-mandibular ligament, and then passes downwards and 

 forwards in the mylo-hyoid groove of the inferior maxilla. The 

 nerve and artery are maintained in position within this groove by 

 an expansion from the lower part of the spheno-mandibular liga- 

 ment, which is attached to the lips of the groove. Thereafter the 

 nerve passes forwards on the inferior surface of the mylo-hyoid 

 muscle, under cover of the superficial part of the submaxillary 

 gland. Having furnished twigs to the mylo-hyoid muscle, it ter- 

 minates in the anterior belly of the digastric. 



(2) The dental branches arise from the parent trunk, whilst it 

 traverses the inferior dental canal. They communicate with each 

 other to form a delicate plexus, from which branches are given 

 oft to the pulps of the lower molar and bicuspid teeth, as well as to 

 the adjacent part of the gum. The pulp-branches correspond in 

 number to the fangs of the teeth, and each enters through a minute 

 opening on the extremity of the fang. 



(3) The mental nerve is one of the two terminal branches. It 

 emerges from the inferior dental canal through the mental foramen. 

 For its distribution, see p. 1177. 



(4) The incisor nerve represents the termination of the inferior 

 dental. It commences at the level of the mental foramen, and 

 passes almost as far as the middle line. Its dental branches com- 

 municate in a plexiform manner, and supply the pulps of the 

 lower canine and incisor teeth, as well as the adjacent portion of 

 the gum. 



Lingual Nerve. — This nerve is sensory. It descends under cover 

 of the external pterygoid muscle, lying anterior and internal to 

 the inferior dental nerve. Whilst under cover of that muscle it 

 receives near its origin the chorda tympani nerve, which joins it 

 from behind at an acute angle, in a direction downwards and for- 

 wards, after emerging from the tympanum through the iter chordae 

 anterius, or canal of Huguier. After issuing from beneath the 

 external pterygoid muscle the lingual nerve j^asses downwards and 

 forwards between the internal pterygoid muscle and the mandibular 

 ramus, and over the mandibular fibres of the superior constrictor 

 muscle. Below the level of the third lower molar tooth it lies im- 

 mediately beneath the mucous membrane of the mouth, and is 



