144 



separately described. After giving off the brancliialis 

 tertiiis, tlie vagus passes backwards and splits into two 

 large nerves. The upper one is the E. intestinalis vagi 

 (r. intest. x.), and the lower one contains the fourth 

 branchial trunk, together with the RE. cardiacus et 

 oesophageus vagi. The upper division gives off two 

 branches, which join the rich oesophageal plexus formed 

 by branches of the lower division, and afterwards passes 

 almost straight backwards as the R, intestinalis, wedged 

 in at first between the kidney, thymus and roof of the 

 oesophagus. It gives off' branches to the oesophagus from 

 time to time, and passes downwards until it lies at the side 

 of the latter structure. It ultimately splits into two, both 

 of which break up in the lateral wall of the opsophagus 

 and are lost before the stomach is reached. 



The lower division, before and after it separates from 

 the R. intestinalis, gives off about 10 mostly motor nerves, 

 which at once form an elaborate plexus in the region of 

 the dorso-lateral wall of the oesophagus. These nerves 

 and others are not shown in the chart. It then passes 

 slightly downwards and backwards, and gives off in front 

 the fourth R. pre-trematicus [pre. 4), which passes sharply 

 downwards and forwards. This at once gives off in front 

 a small motor twig, and then courses straight on to the 

 fourth branchial arch. It was not observed to give off a 

 R. pharyngeus unless an extremely small twig distributed 

 apparently to the side Avail of the pharynx represented 

 that branch. 



After giving off the fourth pre-trematicus, thei lower 

 division turns almost straight dow^nwards, anaVlheif 

 divides into four branches. Two of these pass forwards 

 at once into the ventral wall of the oesophagus, and repre- 

 sent the final derivatives of the R. oesophageus. The third 

 accompanies the inferior pharyngeal bone, and is therefore 



