ROOTS, TRUNK, BRANCHES OF VAGUS NERVE 59 



able numbers; but these are much less numerous than in the 

 vagus trunk. 



8. The recurrent nerve contains an area of large medullated 

 fibers destined for the larynx, and an area of medium and small- 

 sized medullated fibers which are given off in its esophageal, tra- 

 cheal and cardiac branches. 



9. The pharyngeal, superior laryngeal and recurrent nerves 

 take out from the vagus trunk almost all of its large medullated 

 fibers, so that the vast majority of the medullated fibers in the 

 thoracic vagus are either small or medium-sized. These are 

 widely separated by non-medullated fibers. 



10. The non-medullated fibers are present in much greater pro- 

 portion in the thoracic portion of the vagus than in the upper 

 part of the nerve. This is to be accounted for by the fact that 

 a large number of medullated fibers have been taken away by 

 the cervical branches, while practically all of the non-medullated 

 fibers are carried down into the thoracic vagus. This increase 

 in the proportion of non-medullated fibers in the lower part of 

 the nerve is probably also in part due to pre-gangUonic fibers 

 losing their myeUn sheaths in their downward course. 



11. Most of the medullated fibers in the thoracic vagus leave 

 it through the bronchial and esophageal branches, so that the 

 vagus as it passes through the diaphragm may properly be called 

 a non-medullated nerve. It is composed ahnost entirely of non- 

 medullated axons and contains only a few scattered medullated 

 fibers. 



