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separately described. After giving off the branchialis 
tertius, the vagus passes backwards and splits into two 
large nerves. The upper one is the R. intestinalis vagi 
(r. intest. a.), and the lower one contains the fourth 
branchial trunk, together with the RR. cardiacus et 
esophageus vagi. The upper division gives off two 
branches, which join the rich cesophageal 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 
esophagus. It gives off branches to the esophagus 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 esophagus 
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 esophagus. 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 wall of the pharynx represented 
that branch. 
After giving off the fourth pre-trematicus, the lower 
division turns almost straight downwards, and then 
divides into four branches. ‘Two of these pass forwards 
at once into the ventral wall of the cesophagus, and repre- 
sent tbe final derivatives of the R. cesophageus. The third 
accompanies the inferior pharyngeal bone, and is therefore 
