ROOTS, TRUNK, BRANCHES OF VAGUS NERVE 49 



to the fact that the pharjyiigeal and superior laryngeal nerves 

 take out large numbers of medullated fibers from the vagus trunk, 

 allowing the non-medullated fibers to be more closely grouped 

 together. It may in part be due to a real increase in the number 

 of these fibers. Gaskell, who failed to note the presence of non- 

 medullated fibers in the roots of the vagus, but found them in the 

 trunk, concluded that the small medullated fibers in the roots of 

 the vagus and bulbar portions of the accessory ended about cells 

 of the sympathetic type in the ganglion nodosum, and that non- 

 medullated fibers arose from these cells and were continued 

 downward in the trunk of the vagus. Thus he accounted for 

 the non-medullated fibers of the trunk of the vagus as post-gan- 

 glionic autonomic fibers and made the nodose ganglion an auto- 

 nomic ganglion. 



Langley ('03) presents evidence to show that post-ganglionic 

 fibers do not begin in the nodose ganglion, and that all pre-gan- 

 glionic fibers of the vagus end about the cells of ganglia in the 

 peripheral plexuses associated with the vagus. In Shafer's text- 

 book of physiology Langley says that the efferent autonomic 

 fibers of the vagus and the accessory nerves are apparently not 

 connected with the cells of the jugular or nodose ganglia. It is 

 probable that the nerve fibers for each organ end in small ganglia 

 situated in or near the organ itself. He calls attention to Gaskell's 

 observations, that non-medullated fibers appear in the vagus im- 

 mediatel}^ below the nodose ganglion, and concludes that since 

 these can not be post-ganglionic fibers it must follow that either 

 the afferent fibers become non-medullated a long way from their 

 endings, or that the pre-ganghonic fibers lose then- sheaths as 

 they pass downward in the vagus. In the sympathetic system, 

 he says, it can hardly be doubted that pre-ganglionic fibers 

 become non-medullated a considerable distance from the cells to 

 which they run. We ma}^ fairh^ assume that the same may be 

 the case with the similar fibers of the vagus. 



It will be seen that the anatomical data as stated by Gaskell 

 and utilized by Langley in this argument are not strictly correct, 

 since non-medullated fibers are also found in great numbers in 

 the roots of the vagus. But, if the apparent increase in the num- 



THE JOURNAL OF COMPARATIVE NEUROLOGY, VOL. 24, NO. 1 



