PNEUMOGASTRIC NERVE 769 



(4j The muscular branch is distributed to the stylo-pharyngeus inusele. Tliis 

 branch receives a communication from the facial. 



According to Tcstut, tlie glosso-iiliaryngeal gives off carotid branches wliicli join the car()ti<l 

 plexus of the sympathetic and also muscular twigs to the digastric, stylo-hyoid, and stylo- 

 glossus muscles. 



(5) The pharyngeal branches may be two or three in number, and arise from 

 the nerve a short distance below the petrous ganglion. The ])rineipal and most 

 constant of these nerves passes on the outer side of the internal carotid artery, and 

 after a very short independent t-ourse joins the {)haryngeal branch of the vagus to 

 form the pharyngeal plexus with that nerve, and with branches of the superior 

 cervical ganglion. 



(6) The tonsillar branches are a number of small twigs which arise under 

 cover of the hyo-glossus muscle; these proceed to the tonsil, around which they 

 form a plexus. From this plexus fine twigs proceed to the pillars of the fauces 

 and to the soft ]ialate. 



(7) The lingual branches arise from the termination of the nerve and proc(X'd 

 to the dorsum of the tongue, where they are chiefly distributed to the circumvallate 

 })apill8e. Some small twigs pass backwards to the follicular glands of the tongue, 

 and to the anterior surface of its epiglottis. Other twigs are distributed around 

 the foramen caecum, where they communicate with the corresponding twigs of the 

 opposite side. 



TENTH OR PNEUMOGASTRIC NERVE 



Tbe pneumogastric or vagus nerve is the longest of the cranial nerves. It is 

 remarkable for its extensive distril)Ution, for the asymmetry which it shows in 

 certain parts of its course and distribution, and for the almost vertical course whicii 

 it pursues. It sui)j)lies, as its name implies, the lungs and the stomach, but also 

 furnishes branches to the external ear, the pharynx, larynx, oesophagus, trachea, 

 heart, and al)dominal viscera. 



The pneumogastric nerve arises in the medulla in a manner nearly identical 

 with the glosso-pharyngeal nerve, the roots of the former nerve being a serial con- 

 tinuation of the roots of the latter. Thus we find that sensory roots arise from 

 the small-celled nucleus (in a position corresponding to the ala cinerea in the floor 

 of the fourth ventricle), and motor roots arise from the nucleus ambiguus. The 

 latter arch round to join the sensory roots. The vagus is also said to he connected 

 by a few fine filaments with the funiculus solitarius. The roots from tiiese dif- 

 ferent sources unite and pass forwards and outwards to emerge (superficial origin) 

 in the form of from ten to fifteen fasciculi, between the restiform body and the 

 lateral column of the medulla. This row of fasciculi is in series above with the 

 glosso-pharyngeal roots, and below with the bulbar roots of the spinal accessory. 

 The roots of these three nerves cannot be distinguished from one another either at 

 their superficial origin, or at the points where they spi'ing from their nuclei in the 

 medulla, unless the connecticm of the roots Avith their respective trunks has been 

 ])reserved. 



From its superficial origin the vagus nerve proceeds outwards and slightly 

 upwards and forwards beneath the flocculus to reach the jugular foramen. It 

 traverses the middle compartment of the foramen accompanied V)y the spinal 

 accessory and glosso-pharyngeal nerves. The former nerve occupies the same 

 compartment in the dura mater as the vagus. The glosso-])harvngeal is provided 

 with a separate sheath, and is in front of and somewhat internal to the other two 

 nerves. As the vagus traverses the jugular forameiv it bends at a right angle to its 

 former course, and proceeds vertically downwards. In its course down the neck it 

 is placed in front of the rectus ca])itis anticus major and longus colli muscles, but 

 separated from them by the prevertebral layer of the cervical fascia. In the upper 

 part of the neck it is placed between an<l on a ])lane posterioi' to the internal jugular 

 vein and the internal carotid artery. In the lower }>art of the neck it occupies a 

 similar position in regard to the internal jugular vein and conmion carotid artery, 

 the vein being in front and external, and the artery in front and internal to the 

 49 



