ROOTS, TRUNK, BRANCHES OF VAGUS NERVE 53 



at a slight!}^ lower level to run to the stellate ganglion (fig. 1). 

 They are incorporated in the vagus trunk but retain their in- 

 dividuality and do not mix with the vagus fibers. The commu- 

 nications between the recurrent and sympathetic nerves at this 

 level are very complicated and w^e have not been able to work 

 them out satisfactorily. ^\Tiile it is clear that most of the s>Tn- 

 pathetic fibers that join the vagus in the region of the inferior 

 cervical ganglion remain in sharply defined bundles and soon 

 leave the vagus again, it is not possible to be sure that there is 

 not some interminghng of vagus and sympathetic fibers. 



THE PHARYNGEAL BRANCH OF THE VAGUS 



Just above the level of the nodose ganglion the vagus is broken 

 up into several fascicles, as was mentioned in an earlier para- 

 graph. These fascicles branch and reunite forming a compli- 

 cated plexus. The pharyngeal branch arises from one or more 

 of these fascicles. It was not possible to trace the origin of this 

 branch from the bulbar fibers of the accessory, as was done by 

 Molhant in the rabbit. These accessory fibers are so intimately 

 mixed with the vagus fibers in the plexus just described that it 

 is not possible from a study of serial sections in the dog to state 

 whether the fibers of the pharyngeal branch are derived from the 

 bulbar roots of the accessory or not. 



Osmic acid preparations show that the pharyngeal branch is 

 composed for the most part of large medullated fibers, but con- 

 tains also a considerable number of medium and small medullated 

 fibers. Pyridine-silver preparations show that there are few, if 

 any, non-medullated fibers in this branch. 



THE SUPERIOR LARYNGEAL NERVE 



In both osmic acid and silver preparations a large bundle of 

 medullated fibers can be seen leaving the vagus at about the 

 middle of the ganglion nodosum. This is the superior laryngeal 

 nerve. Osmic acid preparations (fig. 7) show that it contains 

 large, medium and small medullated fibers, with the medium 



