986 THE NERVOUS SYSTEM 



sympathetic and form the anterior pulmonary plexus, from which fine twigs pass 

 along the bronchus. 



(b) The posterior bronchial (pulmonary) branches. Almost the entire re- 

 maining trunk of the nerve divides into these branches, which communicate with 

 branches from the second, third, and fourth thoracic ganglia of the sympathetic to 

 form the posterior pulmonary plexus (fig. 706). The plexuses of the two sides 

 communicate freely behind the bifurcation of the trachea, and branches from the 

 plexus pass along each bronchus into the lung. 



(8) The pericardial branches pass from the trunk of the vagus or from the bron- 

 chial or cesophageal plexuses to the anterior and posterior surfaces of the pericardium. 



(9) (Esophageal branches, given off by the trunk of the nerve above the bron- 

 chial plexuses and from the cesophageal plexuses lower down, pass to the wall of the 

 ossophagus. 



(10) Abdominal branches. The terminal part of the left vagus divides into many 

 branches, some of which communicate freely along the lesser curvature of the stomach 

 with filaments from the gastric plexus of the sympathetic, and to some extent with 

 branches of the right vagus, to form the elongated anterior gastric plexus (fig. 706). 

 From this plexus as well as from the nerve-trunk, gastric branches are given to the 

 anterior surface of the stomach. Hepatic branches from the trunk or from this 

 plexus pass in the lesser omentum to the hepatic plexus (fig. 706). The terminal 

 part of the right vagus divides into many branches, and forms along the lesser 

 curvature of the stomach an elongated posterior gastric plexus by communications 

 with branches from the gastric plexus of the sympathetic and with branches from 

 the right vagus. Gastric branches are given off by the trunk of the nerve and 

 from this plexus. Cceliac branches are given by the trunk to the ca-liac (solar) 

 plexus, and splenic and renal branches, either directly or through the crrliac 

 (solar) plexus, are given to the splenic and renal plexuses (fig. 706). 



The Sensory Fibres of the vagus are processes of the cells of the jugular ganglion 

 and the ganglion nodosum. The dendrites of the cells pass peripherally and the 

 axones centrally. The latter enter the medulla in the filaments of attachment in 

 the postero-lateral sulcus, and, in the reticular formation, they bifurcate into ascend- 

 ing and descending branches which end in the nuclei of termination of the vagus, 

 namely, in the nucleus alae cinerea? in the floor of the fourth ventricle and in the 

 nucleus tractus solitarii. 



The Motor Fibres spring from the nucleus ambiguus and join the sensory fibres 

 in the reticular formation. 



Central Connections. The central connections of the vagus are similar to those of the 

 glosso-pharyngeal nerve (fig. 598). Van Gehuchten's observations point to the conclusion that a 

 part of the nucleus of the ala cinerea is a motor nucleus common to the ninth and tenth nerves, 

 and that the only nucleus of termination of the tenth nerve is that of the tractus solitarius. 

 By way of the tractus solitarius, the sensory fibres of the vagus are probably associated with the 

 cells of the cervical segments of the spinal cord which give origin to the phrenic nerve and to 

 motor fibres supplying other muscles of respiration. 



THE ELEVENTH NERVE-THE SPINAL ACCESSORY 



The spinal accessory nerve is exclusively motor. It consists of two parts, the 

 accessory or superior, and the spinal or inferior part. 



The fibres of the accessory or superior portion spring chiefly from the nucleus 

 ambiguus, in common with the motor fibres of the vagus, and they pass through the 

 reticular formation to the postero-lateral sulcus of the medulla, where they emerge 

 as a series of filaments, below those of the vagus. The filaments pierce the pi a mater 

 and unite, as they pass outwards in the posterior fossa of the cranium, to form a 

 trunk which enters the aperture in the dura mater common to the tenth and eleventh 

 nerves. In the aperture this trunk is jpined by the spinal portion of the nerve. 



The spinal or inferior portion arises from the ventro-lateral cells of the ventral 

 horn of the cord as low as the fifth, and rarely the seventh, cervical nerve. The 

 fibres pass dorsalwards and lateralwards from their origins through the posterior 

 part of the ventral horn and through the lateral funiculus of white substance, and 

 they emerge from the lateral aspect of the cord behind the ligamentum denticulatum, 

 along an oblique line, the lower fibres passing out immediately behind the ligament, 

 and the upper close to and sometimes in association with the dorsal roots of the upper 



