Pneumogastric Nerve 69 



it which supply the hinder part of the tongue are concerned in the 

 special sense of taste. 



Arising in the fourth ventricle, the nerve appears between the 

 olive and restiform, and leaves the skull by the jugular foramen. It 

 sends a branch (Jacobson's) to the tympanic plexus, and it enters into 

 the formation of the pharyngeal plexus (p. 138) by passing downwards 

 and forwards between the external and internal carotids. It gives 

 branches also to the stylo-pharyngeus and the tonsil. 



No. 10, the pneumog-astric, or, as it might also be called, cardio- 

 pneumogastric, takes a long and wandering (vagus} course, and holds 

 the medulla in direct association with pharynx and oesophagus ; the 

 larynx, trachea, bronchi, and lungs ; the heart ; the cervical, thoracic, 

 and abdominal sympathetics ; and with the stomach, liver, and spleen. 



It arises from the fourth ventricle and emerges between the olive 

 and restiform, and, having left the skull by the jugular foramen, runs 

 straight down, beneath and between the internal carotid artery and the 

 jugular vein, and then between the vein and the common carotid artery 

 (p. 24 ). Arrived at the root of the neck, it travels onward to the back 

 of the root of the lung, passing on the right side over the beginning of 

 the subclavian artery and behind the vein. On the left it descends 

 between the common carotid and subclavian arteries, behind the left 

 innominate vein, and over the transverse part of the aortic arch. 



At the back of the root of the lung each nerve spreads out into the 

 posterior pulmonary plexus, from which fibres pass into the lung, in 

 company with sympathetic twigs. 



From the back of the roots of the lungs the remnants of the vagi 

 are gathered up into two cords which descend upon the oesophagus 

 (plexus gulce], those of the left side passing, for the most part, on to 

 the front of the stomach, and those of the right on to the back of that 

 viscus. The former branches communicate with the hepatic plexus, 

 and the latter with the splenic and solar plexus. 



As the vagus leaves the skull it gives off the auricular, or Arnolds 

 nerve, which enters the petrous bone near the jugular fossa, and leaves 

 it by the fissure between the external auditory meatus and the mastoid 

 process ; it supplies the skin behind the pinna, and the lining of the 

 auditory meatus. It is generally supposed that the stimulation of this 

 sensory filament by wetting the skin with cold water after a heavy 

 dinner stimulates the pneumogastric to renewed efforts at digestion. 



Ear-cougrb. An important fact in connection with Arnold's nerve 

 is that irritation of its branches, as by a plug of wax, or any foreign 

 body in the meatus, may set up uncontrollable cough. The probable 

 explanation is that there is a communication between this twig and 

 the filaments of the superior laryngeal branch. 



Outside the skull the pneumogastric nerve receives the accessory 

 part of the spinal accessory. Some of the motor filaments which 

 are thus obtained pass out for the pharyngeal plexus, and others 



