THE HEAD AND NECK 1209 



pterygoid. These two branches conduct away all the motor fibres 

 from the long buccal ner\'e, which thereafter is entirely sensory. 



Posterior Division. — ^This division is larger than the anterior, 

 and is almost entirely sensory, the only motor fibres which it con- 

 tains being destined for the mylo-hyoid branch of the inferior 

 dental nerve. Its branches are three in number, namely, (i) auriculo- 

 temporal, (2) inferior dental, and (3) lingual (gustatory). 



Auriculo-temporal Nerve. — ^This nerve, which is sensory, arises 

 by two roots, between which the middle meningeal artery ascends 

 to the foramen spinosum. Thereafter the two roots join, and the 

 nerve is directed backwards under cover of the external pterygoid 

 muscle. Having passed close behind the temporo-mandibular 

 joint to the interval between that joint and the auricle, it enters 

 the upper part of the parotid gland. It then changes its course, 

 and passes upwards through the upper part of the gland, after 

 emerging from which it crosses tne zygoma and ascends close 

 behind the superficial temporal artery to end in its terminal tem- 

 poral branches. 



Branches of Communication. — (i) Each root of the auriculo- 

 temporal nerve receives a small branch from the otic ganglion. 

 These branches contain fibres of the glosso-pharyngeal nerve, through 

 means of (a) its tympanic branch (Jacobson's nerve), (b) the 

 tympanic plexus, and (c) the small superficial petrosal nerve, which 

 latter is reinforced by a branch from the geniculate ganglion of the 

 facial nerve. These glosso-pharyngeal fibres are destined for the 

 parotid gland. (2) Two communicating branches pass to the 

 temporo-facial division of the facial nerve in the parotid gland. 



Branches of Distribution. — (i) Articular branches enter the tem- 

 poro-mandibular joint through the back part of the capsule. 



(2) Glandular branches are distributed to the parotid gland, to 

 which they conduct fibres of the glosso-pharyngeal nerve. 



(3) Meatal branches, upper and lower, enter the meatus auditorius 

 extemus between its cartilaginous and osseous parts, and supply 

 the skin which lines it, the upper branch also giving twigs to the 

 outer layer of the membrana t^Tnpani. (4) Anterior auricular 

 branches are distributed to the skin of the tragus and the upper 

 part of the outer surface of the auricle. The distribution of the 



: meatal and auricular branches explains why .pain, due to affections 



I of the lower teeth, may be referred to the ear canal and auricle. 



! (5) The temporal branches are terminal. They accompany the 



I branches of the superficial temporal artery, and supply the skin 



of the temporal region as high as the vertex of the skull. They 



communicate with the temporal branches of the facial, and the 



temporal branch of t le temporo-malar from the superior maxillary 



nerve. 



Inferior Dental Nerve. — This nerve, though chiefly sensory, con- 

 tains motor fibres, which, however, leave it in its mylo-hyoid branch. 

 It passes downwards, being at first under cover of the external 

 pterygoid muscle. After escaping from beneath that muscle, it 



