THE HEAD AND NECK 1073 



Posterior Auricular Nerve. — ^This is a branch of the facial 

 nerve immediately after it emerges from the aqueduct ot Fallo- 

 pius through the stylo-mastoid foramen. It passes upwards 

 between the mastoid process and the auricle, where it lies deeply 

 in company with the posterior auricular artery, and it divides into 

 two branches — auricular and occipital. The auricular branch 

 supplies the retrahens auriculam muscle on its deep aspect, and 

 those intrinsic muscles of the auricle which lie on its inner or cranial 

 aspect. It may also send a branch upwards beneath the retrahens 

 auriculam to supply the posterior part of the attollens auriculam. 

 The occipital branch passes backwards, and supplies the corresponding 

 half of the occipitalis muscle. The posterior auricular nerve com- 

 municates with the small occipital and great auricular ner\'es, and 

 also with the auricular branch (Arnold's nerve) of the pneumo- 

 gastric. 



Nerve of Arnold. — ^This is the auricular branch of the ganglion 

 of the root of the pneumogastric ner\-e. Ha\'ing traversed the 

 auricular canaliculus in the petrous part of the temporal bone, it 

 emerges through the auricular or tjnipano-mastoid fissure, between 

 the mastoid process and tympanic plate, and thereafter divides into 

 two branches — auricular and communicating. The auricular branch 

 takes part in the supply of the inner or cranial surface of the auricle, 

 and also supplies the lower and back part of the meatus auditorius 

 extemus ; and the communicating branch joins the posterior auricular 

 ner\'e. 



Posterior Auricular Artery. — ^This vessel is one of the t\vo pos- 

 terior branches of the external carotid artery, the other branch 

 being the occipital artery. Having passed backwards and upwards 

 under cover of the parotid gland, it lies deeply bet\veen the mastoid 

 process and the auricle, in close relation to the posterior auricular 

 nerve, and divides into two branches — auricular and mastoid. 

 The auricular branch supplies the inner or cranial surface of the 

 auricle and adjacent structures, and it anastomoses with the pos- 

 terior branch of the superficial temporal artery. The mastoid 

 branch passes backwards to the corresponding half of the occipitalis 

 muscle, and anastomoses with the occipital artery. 



The posterior auricular vein is of fairly large size, and returns the 

 blood from the lateral portion of the scalp posteriorly, and the 

 inner surface of the auricle. Its radicles communicate with the 

 occipital plexus and with the posterior branch of the superficial 

 temporal vein. The vessel passes downwards and forwards over 

 the upper part of the stemo-cleido-mastoid muscle, and terminates 

 about the level of the angle of the lower jaw by joining the posterior 

 division of the temporo -maxillary vein to form the external jugular 

 vein. 



Posterior Auricular, or Mastoid, Glands. — These glands lie close 

 to the insertion of the stemo-cleido-mastoid muscle. They receive 

 their afferent hmphatics from the lateral part of the back of the 

 scalp and the back of the auricle, and their efferent IjTiiphatics pass 

 tu the superficial cervical glands. 



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