958 THE NERVOUS SYSTEM 



(9) CEsophageal branches, given off by the trunk of the nerve above the bronchial plexuses 

 and iFrom the oesophageal plexuses lower down, pass to the wall of the oesophagus. 



(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. 744). From this plexus as well as from the 

 nerve-trunk, gastric branches are given to the anterior surface of the stomach. Hepatic 



V branches from the trunk or from this plexus pass in the lesser omentum to the hepatic plexus 



\\ (fig. 744). The terminal part of the right vagus divides into many branches, and forms along 



K. ] the lesser curvature of the stomach an elongated posterior gastric plexus by communications 



By with branches from the gastric plexus of the sympathetic and with branches from the right vagus. 



f/ Gastric branches are given off by the trunk of the nerve and from this plexus. Coeliac branches 



are given by the trunk to the coehac (solar) plexus, and splenic and renal branches, either 



directly or through the coeliac (solar) plexus, are given to the splenic and renal plexuses (fig. 744). 



Central connections. — The sensory fibres of the vagus are processes of the cells of the jugular 



ganglion and the ganglion nodosum. The peripheral fibres from these cells bring in sensory 



impulses from the periphery, and their central fibres convey the impulses to the brain. The 



latter fibres enter the medulla in the filaments of attachment in the postero-lateral sulcus, and, 



I in the reticular formation, they bifurcate into ascending and descending branches which end in 



I the nuclei of termination of the vagus, namelj'-, in the nucleus alse cinerese in the floor of the 



fourth ventricle and in the nucleus tractus solitarii. The tractus solitarius consists largely of the 



descending branches. These and the axones arising from the nuclei of termination of the vagus 



descend the spinal cord to terminate about ventral horn cells which give origin to the phrenic 



nerve and to motor fibres supplying other muscles of respiration, and they also convey impulses 



which are distributed to visceral motor neurones along the spinal cord. 



The motor fibres spring from the nucleus ambiguus and from the dorsal efferent (motor) 

 nucleus of the vagus, described on page 820. They join the sensory fibres in the reticular 

 formation. Some of the motor fibres, especially those from the dorsal efferent nucleus, are 

 visceral motor fibres. 



The central connections of the vagus are similar to those of the glosso-pharyngeal nerve 

 (fig. 647). Van Gehuchten's observations point to the conclusion that the chief nucleus of 

 termination of the vagus nerve is that of the tractus solitarius. 



THE SPINAL ACCESSORY NERVE 



The spinal accessory nerve [n. accessorius] is exclusively motor. It consists of 

 two parts, the accessor}^ or superior, and the spinal or inferior part. 



The fibres of the accessory or superior portion [ramus internus] ("accessory 

 vagus") spring chiefly from the inferior continuation of the nucleus ambiguus, in 

 common with the motor fibres of the vagus above, 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 pia 

 mater and unite, as they pass outward in the posterior fossa of the cranium, to 

 form a part of the nerve which enters the aperture in the dura mater common to 

 the vagus and spinal accessory nerves. In the aperture this trunk is joined by the 

 spinal portion of the nerve. 



The spinal or inferior portion [ramus externus] 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 dorsalward and lateralward from their origins 

 through the lateral 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 dorsal to the ligament, and the upper close to and sometimes in 

 association with the dorsal roots of the upper two spinal nerves. As the spinal 

 fibres pass out of the surface of the cord they unite to form an ascending strand 

 which enters the posterior fossa of the cranium, through the foramen magnum, 

 and, turning lateralward, blends more or less intimately with the accessory por- 

 tion. Thus combined, the nerve enters the jugular foramen in company with the 

 vagus, but here it is again separated into its two branches, which contain chiefly 

 the same fibres as the original superior and inferior parts. 



The superior branch, or accessory portion of the nerve, gives one or more filaments to the 

 jugular ganglion (ganglion of the root of the vagus), and then joins cither the trunk of the vagus 

 directly or its ganglion nodosum, the fibres of the branch being contributed to the i)haryngeal, 

 laryngeal, and cardiac branches of the vagus. Fibres corresponding to the white rami communi- 

 cantes, ab.scnt in the cervical nerves, probably enter the cervical sympathetic ganglion through 

 this ramus of the spinal acces.sory nerve. The fil)res from the accessor}' to tlie vagus therefore 

 probal)ly include visceral motor and cardio-iiiliiljifory fibres. 



The inferior branch or the spinal portion runs backward and downward under cover of the 

 posterior l.-elly of the digastric and the sterno-niastoid. It usually crosses in front of and to 

 the lateral side of the internal jugular vein and between it and the occipital artery; then it 



