No. I.] THE CRANIAL NERVES OF AMPHIBIA. 199 



a direct continuation of the dorsal funiculus of the cord. It 

 consists principally of fine, with a few medium-sized, fibres. 



The Vagus roots fall into two divisions. The four roots 

 emerging farthest caudad terminate internally in the "upper 

 lateral ganglion," which is a continuation of the dorsal column 

 of cells in the cord. The four roots emerging most cephalad 

 have the same internal termination as the Acusticus. 



The terminal nuclei of the Acustico-faciahs, and the four 

 roots just mentioned, lying as they do above the ascending 

 Trigeminus and upper lateral ganglion, which represent con- 

 tinuations of the cord, are thus, according to Ahlborn, some- 

 thing superadded in the medulla oblongata, and are equivalent 

 to the higher brain centres. They are not represented by any 

 portion of the cord, or, at the most, by a very small band mesad 

 of the dorsal funiculus, of which band one can only say that it 

 exists. The nucleus of the Faciahs lies well above and sepa- 

 rated from that of the Acusticus. The cells in it are small and 

 the fibres of the Facialis issuing from it are fine and of a very 

 uniform size. The Acusticus emerges in two roots, one above 

 the other. 



Of the IX + X roots, the four composing the first (cephalic) 

 set unite to form R. branchiahs I, which sends a twig to the 

 Hypoglossus. The first two of the second set are joined by a 

 recurrent branch from the Facialis to form the fine-fibred 

 N. lateralis. The last two roots form the Pneumogastricus, 

 which is connected with the N. lateralis through the ganglion 

 of the same. 



The first fact that impresses one in this arrangement is that 

 the first set of roots from the Acusticus region do not form 

 the N. lateralis, but the R. branchialis I. Furthermore, the 

 N. lateralis is formed partly by a recurrent branch from the 

 Facialis passing around outside the auditory capsule — a thing 

 which does not occur in the N. lateralis in the higher forms. 

 Again, on comparing the course of the N. lateralis with the 

 arrangement of the pits, it is evident that only a small pro- 

 portion of them would be innervated by this nerve, which has 

 a position near the mid-dorsal line. When these facts are con- 

 sidered — especially the non-derivation of this nerve from the 



