THE PNEUMO-GASTBIC NERVE. 69 



extend along the ramifications of the air-tube through the substance of the lung, 

 where they are beset with minute ganglia. 



The anterior and posterior pulmonary plexuses of the two sides communicate with 

 one another in an open network across the front and back respectively of the lower 

 end of the trachea, and through these networks fibres are conveyed from both 

 pneumo-gastric nerves into each lung. 



CEsophageal branches. The oesophagus within the thorax receives branches 

 from the pneumo-gastric nerves, both above and below the pulmonary branches. 

 The lower branches are the larger, and are derived from the oesophageal plexus, 

 formed by connecting cords between the nerves of the right and left sides, while 

 they lie in contact with the oesophagus. 



Fericardial branches. Either vagus may furnish a filament to the upper and 

 fore part of the pericardium. Other twigs pass regularly to the back of the pericar- 

 dium from the oesophageal plexus, and often from the posterior pulmonary plexuses 

 (Zuckerkandl). 



Gastric branches. The branches distributed to the stomach (gastric nerves} 

 are terminal branches of both pneumo-gastric nerves. The nerve of the left side, 

 on arriving in front of the oesophagus, opposite the cardiac orifice of the stomach, 

 divides into many branches : the largest of these extend over the fore part of the 

 stomach ; others lie along its small curvature, and unite with branches of the right 

 nerve and the gastric plexus of the sympathetic ; and some filaments are continued 

 between the layers of the small omentum to the hepatic plexus. The right pneumo- 

 gastric nerve descends on the back of the gullet to the stomach, and distributes 

 branches to the posterior surface of the organ : a large portion of this nerve passes 

 to the solar, splenic and left renal plexuses of the sympathetic. 



SUMMARY. The pneumo-gastric nerves convey motor fibres to the voluntary 

 muscles of the soft palate (with the exception of the tensor palati), pharynx and 

 larynx, these being in part at least derived originally from the spinal accessory, to 

 the unstriped muscle of the alimentary canal oesophagus, stomach and intestine (with 

 the exception of the rectum), and of the air-passages trachea, bronchi, and their 

 divisions in the lungs. Sensory fibres are furnished to the pharynx, oesophagus and 

 stomach, to the larynx, trachea and bronchial ramifications, as well as to the dura 

 mater, the external ear, and the pericardium. The vagi also supply nerves to the 

 heart, both efferent (inhibitory also received from the spinal accessory) and 

 afferent (depressor), and possibly inhibitory dilator fibres to the vessels of the intes- 

 tine. Lastly, pneumo-gastric fibres pass, either directly or through the solar plexus 

 and its offsets, to the liver, pancreas, spleen, kidneys and suprarenal bodies. Each 

 pneumo-gastric nerve is connected with the following cranial nerves the spinal 

 accessory, glosso-pharyngeal, facial, and hypoglossal ; also with some spinal nerves ; 

 and with the sympathetic in the neck, thorax and abdomen. 



XI. SPINAL ACCESSORY NERVE. 



The eleventh or spinal accessory nerve (spinal nerve accessory to the vagus) con- 

 sists of two parts, the one of which (bulbar or accessory) joins the trunk of the 

 pneumo-gastric, while the other (spinal) is distributed to the sterno-mastoid and tra- 

 pezius muscles. Its fibres spring from a continuous column of cells extending from 

 the level of the lower third of the olive to the fifth cervical nerve, in the bulb placed 

 dorso-laterally to the hypoglossal nucleus, and in the spinal cord forming a part of the 

 ventro-lateral group of the anterior horn. From this nucleus the fibres are directed 

 at first dorsally for a short distance, and then turn outwards through the lateral 

 region of the bulb or cord to emerge in a series of filaments from the side of the 



VOL. III. PT. 2. S 



