CRANIAL NERVES 133 



fibers may serve more than one of the modahties of sense as centrally 

 analyzed. 



The peripheral fibers of this system are usually described as the 

 general cutaneous component of the nerves, though some of them are 

 distributed to deeper tissues. Most of them enter the brain in the 

 trigeminus root and smaller numbers in roots of the VII, X, and 

 (probably) IX nerves. The vagal fibers of this system have wide 

 peripheral distribution (Coghill, '02), including the ramus auricularis 

 and other vagal branches and also anastomotic connections with 

 branches of the IX and VII nerves. The peripheral distribution of the 

 VII fibers has not been described. A few fibers of the sensory IX root 

 have been seen (rarely) to descend in the spinal V fascicles. Most 

 urodeles are said to lack a general cutaneous component of the IX 

 nerve, though there is some evidence of it in Necturus ('30, p. 22). 

 If the presence of these fibers is confirmed, they probably join the 

 general cutaneous component of the vagus peripherally. 



Many of the trigeminal fibers divide immediately upon entering 

 the brain into the thick descending branches of the spinal V root and 

 thinner ascending branches (fig. 40) of the cerebellar root. The long- 

 est course that can be taken by one of these bifurcated fibers is 

 shown in figure 3. Some of these fibers take deeper courses, penetrat- 

 ing the spinal V root to enter the fasciculus solitarius (p. 148). Some 

 of the mesencephalic V fibers also divide near their exit from the 

 brain, with descending branches arborizing in the reticular formation 

 of the upper medulla oblongata (p. 141 and fig. 13). 



The spinal V root is large and well myelinated. It can readily be 

 followed through the length of the medulla oblongata and for an 

 undetermined distance into the spinal cord (figs. 87-90). Each of its 

 fibers for its entire length is provided with a fringe of short collaterals 

 (fig. 38), which are directed inward into a neuropil which is con- 

 tinuous dorsally with that similarly related with the VIII and lateral- 

 line roots, the whole forming^a common pool for the reception of all 

 somatic sensory components (fig. 9). In the calamus region these col- 

 laterals mingle with collaterals and terminals of spinal root fibers of 

 the dorsal funiculus and the spinal vestibular root, bulbar correlation 

 tracts a and b, and the dorsolateral funiculus. This axonic neuropil is 

 permeated by dendrites of the nucleus of the dorsal funiculus and 

 commissural nucleus of Cajal. 



In many of our Golgi preparations the central courses of the sen- 



