44(5 DR. C. F. SONNTAG O.N THE 



vagus gives oil' two tliinmn- l^iaiicbcs whicli l)i'enk up into several 

 twigs to a deep cardiac plexus. 



6. Pulmonary Nerves (text-tigs. 20 & 21, f/ and y') : — The left 

 vagus gives off two anterior pulmonary nerves before it passes to 

 the dorsal surface of the root of the left lung {g'). On the dorsal 

 surface of the pulmonary root it gives off three posterior 

 pulmonary nerves [g). The right vagus gives off one anterior 

 pulmonary nerve under cover of the vena azygos major, where it 

 curls over the root of the right lung to join the superior vena 

 cava. Behind the pulmonary root it divides into two branches. 

 One of tliese (h) is distriljuted to the posterior pulmonary plexus, 

 and then rejoins the other division. 



7. (Esojyhageal nerves (text-fig. 21, O.N) : — The left vagus gives 

 oft' several oesophageal branches which form a plexus guhie. The 

 right vagus gives an ascending oesophageal nerve (O.N'j, and some 

 small bivanches which anastomose with those of the left nerve. 



The left vagus runs through theventi-al part of the oesophageal 

 opening in the diaphragm, and the right vagus runs tlirough the 

 dorsal part. A complicated series of anastomoses between their 

 branches takes place in the posterior part of the thorax (text- 

 lig. 20). 



"The left vagus gives many branches to the esophagus and 

 ventral surface of the stomach, and twigs can be traced into the 

 splenic and superior mesenteric plexuses. Communications can 

 also be traced to the left splanchnic nerves (text-fig. 22). 



The right vagus supplies the doi'sal surface of the stomach, and 

 bi-anches run to the solar plexus (text-fig. 21). 



No direct communications run between tlie vagus and phrenic 

 nerves. 



The Spinal Accessory Nerve (text-fig. 19, xi) has the usual 

 relations to other nerves at its emergence from the foramen 

 lacerum posticum. It lies on the dorsal aspect of the sterno- 

 mastoid and cleido-mastoid, and it gains the deep sui'face of the 

 trapezius. It passes postero-laterally and runs over the dorsum 

 of the scapula between the ventral border and root of the spine. 

 It can be traced into the most posterior fibres of the trapezius. 



It forms a rich plexus vi'ith the cervical nerves, and com- 

 munications run between it and the ninth, tenth, and twelfth 

 nerves. 



The Hypoglossal iVeri'e (text-fig. 19,xii) communicates with the 

 other nerves at the base of the skull and describes a wide loop. 

 Reaching the tongue by passing on the surface of hyoglossus it 

 divides into two branches. One is more superficial, and gives off 

 numerous fine muscular twigs. The other is deeper and thicker, 

 and can be traced almost to the tip of the tongue. Before it 

 divides, the hypoglossal gives off the descendens (D.H) nerve and 

 communicates with the lingual nerve. The former enters as 

 usual into the ansa hypoglossi. 



In text-fig. 19 the three distinct nerve supplies to the tongue 

 are shown. 



