258 yournal of Comparative Neurology and Psychology. 



I find this component leaving the vagus ganghon as a distinct 

 nerve and passing out a considerable distance before it unites with 

 the glossophar) ngeus just before the latter gives off the r. com- 

 municans X ad VII. The fibers of this nerve, w^ithin the ganglion, 

 have all the appearance of sensorv^ fibers; and since, as stated 

 above, there appear to be no motor fibers in the general cutaneous 

 root of the vagus, one seems to be justified in interpreting this 

 component of the glossopharyngeus as sensory. Furthermore 

 this is the only interpretation which will account for the fibers of 

 this nerve which have a general cutaneous distribution. On any 

 other supposition one would have to assume that communis fibers 

 have a general distribution to the skin without relation to sense 

 buds — a supposition which would scarcely be w^arranted by our 

 present knowledge of nerve components. 



The general cutaneous component of the glossopharyngeus in 

 Amblystoma is distributed to the skin of the first external gill and 

 over the base of this structure, and through the r. communicans 

 to the r. jugularis VII. In the absence of the external gill in the 

 adult Triton, a general cutaneous branch of this nerve is distrib- 

 uted to a corresponding region and, as explained below, there is 

 good proof that the remamder of the general cutaneous com- 

 ponent of the glossopharyngeus enters the r. communicans 

 X ad VII. 



J. The Ramus Communicans X ad VII . — It is impossible for 

 me to trace the axones of this nerve with perfect certainty to their 

 origin in the nerve roots and thus to determine its composition 

 beyond dispute as I have done in the case of Amblystoma; but in 

 the case cited above, in which the vagus component of the glosso- 

 pharyngeal trunk joins the latter just before the r. communicans 

 is given ofi^, there is a space of only ten sections ten micra thick 

 in which it is impossible to distinguish the vagus component or 

 the r. communicans clearly from the rest of the nerve. This 

 indistinctness is due to the tortuous course of the nerve at and near 

 this point of flexure ventrad where the r. communicans arises. 

 However, a study of the position which the vagus component takes 

 in the trunk and of the point of origin of the r. communicans 

 makes it almost certain that the r. communicans is derived, at 

 least in part, from the vagus component. 



As the r. communicans passes cephalad to join the r. jugularis 

 VII, it gives off no fibers to any muscle, but it meets fibers from 



