536 NERVOUS SYSTEM 



a downward direction and go to the liver, and with another branch run- 

 ning between the folds of the gastro-hepatic omentum, they follow the 

 course of the portal vein in the hepatic substance. The branches 

 of this nerve anastomose with the nerve of the right side and with the 

 sympathetic. 



The right pneumogastric, situated posteriorly, at the oesophageal 

 opening of the diaphragm sends a few filaments to the muscular coat 

 and the mucous membrane of the stomach, passes backward and is dis- 

 tributed to the liver, spleen, kidneys, suprarenal capsules and finally to 

 the entire small intestine. From the splenic plexus, filaments derived 

 from the pneumogastric go to the pancreas. Before the nerves pass to 

 the intestines, there is a free anastomosis and interchange of filaments 

 between the right and the left abdominal branches. 



General Properties of the Roots of Origin of the Pneumogastrics. 

 The sensibility of the pneumogastrics in the neck, while it is dull as 

 compared with the properties of other sensory nerves, is nevertheless 

 distinct. It is impossible, however, to expose the roots of the nerves in 

 living animals before they have received communicating motor filaments, 

 without such mutilation as would interfere with accurate observations ; 

 but in animals just killed, if the roots are exposed arnd divided so as to 

 avoid reflex movements, and if care is taken to avoid stimulation of 

 motor filaments from adjacent nerves, it is found that the application 

 of electricity to the peripheral end of the root from its origin to the 

 ganglion gives rise to no movements. It may therefore be assumed 

 that the true filaments of origin of the pneumogastrics are exclusively 

 sensory, or at least that they have no motor properties. 



Properties and Uses of the Auricular Nerves. The auricular nerves 

 are sometimes described with the facial and sometimes with the pneu- 

 mogastric. They contain filaments from the facial, the pneumogastric 

 and the glosso-pharyngeal. The sensory filaments of these nerves give 

 sensibility to the upper part of the external auditory meatus and to the 

 membrana tympani. The meatus also receives filaments from the 

 trifacial. 



Properties and Uses of the Pharyngeal Nerves. The pharyngeal 

 branches of the pneumogastric are mixed nerves, their motor filaments 

 being derived from the spinal accessory ; and their direct action on the 

 muscles of deglutition belongs to the physiological history of the last- 

 named nerve. As already stated in treating of the spinal accessory, 

 the filaments of communication that go to the pharyngeal branches of 

 the pneumogastric are distributed to the pharyngeal muscles. 



It is impossible to divide all the pharyngeal filaments in living ani- 

 mals and observe directly how far the general sensibility of the pharynx 



