No. I.] THE CRANIAL NERVES OF AMPHIBIA. 115 



ganglionated nerves (as the root in question will be seen below 

 to be), must be considered now to be merely a physiological 

 and not an anatomical one. It is obvious, from more recent 

 investigations, that the only cells with which the fibres of 

 such roots are directly connected are those of the peripheral 

 ganglia belonging to these roots. 



This being the case, it will be convenient to denominate 

 such internal nuclei, whose cells are not directly continuous 

 with the root fibres, ''terminal nuclei," in distinction to those 

 nuclei whose cells are in direct continuity with root fibres 

 (ganglia of sensory roots and motor nuclei), which may be 

 called "nuclei of origin." This distinction and terminology is 

 that adopted by Kolliker in his Gewebelehre (34) ('' Endkern " 

 and " Ursprungskern "). 



In the tadpole it is difficult to determine whether some of the 

 acoustic fibres may not be similar to those of the dorsal VII. 

 From appearances in the tadpole, and from the fact that in the 

 frog the origin of a portion of the VIII is ascribed to similar 

 ganglion cells (Koppen), even from the mere fact of the per- 

 sistence of these cells after the disappearance of the dorsal 

 VII, this similarity might be inferred. 



This root, the dorsal VII, already reduced in the tadpole, 

 disappears in adult Anura. The reasons for this disappearance 

 will become evident when its distribution is considered. It 

 may be well to point out here that this fact has caused some 

 confusion and apparent discrepancy in the accounts of the 

 Facialis by different observers, some of whom assert the origin 

 of the VII to be dorsal to the VIII, while others assert it to be 

 ventral. The latter refer to forms in which the dorsal VII has 

 disappeared; the former overlook the ventral portion of the 



VII. Koppen (35), however, overlooking the ventral portion 

 in the frog, in which the dorsal root is lost, is obliged to look 

 for the VII in the Trigeminus. He is further misled by expect- 

 ing to find the Facialis a purely motor nerve. 



At 852 d= the ventral roots of the VII separate from the 



VIII, the coarse-fibred root (VII ah) forming the outer and 

 lower portion of the bundle. The description of the dorsal 

 VII will be taken up first. 



