52 Journal of Comparative Neurology. 



In describing the VII root Ahlborn has entirely over- 

 looked the fasciculus communis root and described only the 

 dorsal root, which arises from a nucleus " welcher iiber den 

 Acusticuskernen im obersten Rand der Hirnwand liegt, da, wo 

 dieser im Begriff ist, in das Cerebellum iiberzugehen." This is, ■ 

 as shown*above, a lateral line root and there is besides a more 

 ventral lateral line root apparently overlooked by Ahlborn. 

 The formation of the VII-X anastomsis from the ganglion of 

 these roots has been properly described by Ahlborn. His fail- 

 ure to find the fasciculus communis root has misled later au- 

 thors, especially with regard to the homology of the ramus 

 lateralis vagi. 



Miss Alcock ('98) has described the distribution of fibers 

 innervating lateral line organs by way of rami of VII, IX and 

 X, and reaches the conclusion that the lateral line nerves do not 

 form a separate system but form an essential part of each 

 branchial nerve. This contention ignores the whole tendency 

 of recent investigations to analyze the cranial nerves into com- 

 ponents according to their function, as shown by central con- 

 nections and peripheral distribution, and requires no further dis- 

 cussion. Her description of the nerves I have verified for the 

 most part, but there are certain additions and corrections to be 

 made to her description of the roots from which the nerves are 

 derived. She has overlooked the fact that the fibers in the 

 vagus which supply lateral line organs are derived from the 

 VII-X anastomosis, and hence have no relation whatever, 

 morphological or physiological, with the fasciculus communis 

 fibers, except that they happen to run in the same trunk. She 

 does not describe the ganglion of IX or its relation to that of 

 the lateral line nerve, although she clearly states that the latter 

 is entirely distinct from that of X proper. If we assume that 

 the conditions are the same as in Petromyzon planeri and Lam- 

 petra, she has probably failed to analyze the ganglia of the post- 

 auditory lateral line and IX roots and so failed to recognize the 

 origin of the lateral line component of the IX trunk from a 

 true lateral line root. It is certain that IX has no more con- 

 nection with the lateral line system than X has. In describing 



