772 THE NERVOUS SYSTEM 



(a) The meningeal or recurrent branch is a slender filament which is given 

 off from the ganglion of the root. It takes a recurrent course through the jugular 

 foramen, and is distrihutcd to the dura mater around the lateral sinus. 



{b) The auricular branch, or nerve of Arnold, arises from the ganglion of the 

 root in the jugular t'oranien. It traverses the Ixtne, ])assing to the inner side of the 

 a(jueduct of P^allo{)ius; forming a connnunication with the facial nerve, and emerges 

 hehind the pinna, wliere it divides into two hranches, one of Avhich joins the pos- 

 terior auricular branch of the facial while the other supplies the posterior and 

 inferior part of the external auditory meatus and the back of the pinna. It also 

 supplies twigs to the osseous part of the external auditory meatus and to the lower 

 ])art of the outer surface of the membrana tympani. 



(c) The pharyngeal branches may be two or three in number. The ])rin(ii)al 

 of these joins the pliaryngeal branch of the glosso-pharyngeal in front of the internal 

 carotid artery, and passes witli the latter behind the external carotid artery down- 

 wards and inwards to reach the j^osterior aspect of the pharynx. Here the two 

 nerves are joined by branches from the superior cervical ganglion of the sympa- 

 thetic, and form, with the latter, the pharyngeal plexus. 



(d) The superior laryngeal nerve arises from the lower part of the ganglion 

 of the trunk, and passes obliquely downwards and inwards behind and internal to 

 both internal and external carotid arteries towards the larynx. In this course it 

 describes a curve with the convexity downwards and outwards, and divides into 

 (i) a larger internal and (ii) a smaller external branch. Before its division it is 

 joined by communications from the sympathetic and from the pharyngeal plexus. 



(i) The internal branch accompanies the superior laryngeal artery to the interval 

 between the ui)per border of the thyroid cartilage and the great cornu of the hyoid 

 bone. It passes uhder cover of the thyro-hyoid muscle and pierces the thyro-hyoid 

 membrane to gain the interior of the larynx; here it divides into a number of 

 diverging branches. The ascending branches supply the mucous membrane on 

 both surfaces of the epiglottis. The descending branches ramify in the mucous 

 membrane lining the larynx, communicate with the recurrent laryngeal nerve, and 

 supply the mucous meml)rane which covers the back of the cricoid cartilage. 



(ii) The external laryngeal branch runs downwards towards the lower border 

 of the thyroid cartilage. It pierces the lower fibres of the inferior constrictor of 

 the pharynx, and ends for the most part in the crico-thyroid muscle. A fcAV fila- 

 ments pierce the crico-thyroid membrane, and are distributed to the lining mem- 

 brane of the larynx. It gives off a cardiac branch which joins one of the cardiac 

 branches of the sympathetic; it also furnishes twigs to the inferior constrictor and 

 communicating twigs to the pharyngeal plexus, and it receives a comnumication 

 from the superior cervical ganglion of the sympathetic. 



(e) The inferior or recurrent laryngeal nerve of the right side arises at the 

 root of the neck in front of the first stage of the right subclavian artery. It hooks 

 round the artery, passing l)elow and then behind that vessel, and runs upwards and 

 slightly inwards, crossing obliquely behind the conunon carotid artery. Having 

 gained the side of the trachea, it runs u})wards in the groove between that canal 

 and the fpsophagus, accompanied by the inferior thyroid artery, and enters the 

 larynx by passing under cover of the lower border of the inferior constrictor of 

 the pharynx. It then breaks up into branches, which are distributed to all the 

 intrinsic muscles of the larynx with the exception of the crico-thyroid, and it 

 communicates, as above mentioned, with the superior laryngeal nerve. Near its 

 commencement it usually gives off a cardiac branch. 



In its course between the oesophagus and trachea it gives numerous twigs to 

 these structures, and near the termination it furnishes one or two twigs to the 

 inferior constric-tor of the ])harvnx. 



On the left side the nerve arises in front of the aortic arch, and winds round 

 the concavity of tlu; arch just behind the obliterated ductus arteriosus. It crosses 

 obliquely behind the root of the left common carotid artery, gains the angular 

 interval between the o}sophagus and trachea, and corresponds to the nerve of the 

 right side for the remainder of its course and distribution. 



(/) Cardiac branches. — These are named (from the different levels at which 



