1 68 Journal of Comparative Neurology. 



the latter. In passing from IX to VII ganglia the sympathetic 

 runs external to the ear capsule. 



The various components can be followed with great pre- 

 cision proximally in the root portions and through the ganglia 

 of the cranial nerves. Throughout the peripheral courses of 

 the nerves the analysis is somewhat more difficult, but has been 

 satisfactorily accomplished in all but a very few cases. The 

 naked organs of the lateral line series (pit lines) and the terminal 

 buds of the skin (communis system) are sometimes hard to dif- 

 ferentiate because their nerve fibers are intermediate in size be- 

 tween the exceedingly large fibers typical for the lateralis system 

 and the very small communis fibers. The general cutaneous 

 system of nerves is, however, as clearly separable from the 

 others peripherally as it is centrally. And this is important in 

 many ways. For example, it will materially assist in the at- 

 tempt to homologize cranial and spinal nerves to know that not 

 all sensory cranial roots are comparable with spinal dorsal roots. 

 It is, e. g. , no longer legitimate to homologize lateral line roots 

 with dorsal spinal roots. The latter are represented in the 

 brain mainly by the spinal V or general cutaneous system, and 

 the special cutaneous systems (terminal bud and lateralis) are 

 probably neomorphs in the head, as Strong has maintained. 



If cranial and spinal nerves were derived from a common 

 type, the common ancestral nerve probably contained two kinds 

 of sensory fibers, viz. general cutaneous and general visceral. 

 Both of these kinds of fibers appear to be present in the dorsal 

 roots of Amphioxus and of the spinal nerves of Craniota. 

 Two of the cranial nerves retain the general cutaneous fibers 

 (viz. X and V) ; the others seem to have lost them. The vis- 

 cero-sensory fibers have either been lost or rendered unrecog- ' 

 nizable on account of their extreme specialization in all but the 

 X, IX and VII nerves. In these nerves they have been cen- 

 tralized to form the communis system and hypertrophied to 

 serve a double purpose : (i) The viscero-sensory nerves of the 

 trunk seem to have been in large measure supplanted by the r. 

 intestinalis vagi. (2) In the cephalic end of the digestive tract 

 more highly specialized sense-organs (taste buds) have been de- 



