No. I.] THE CRANIAL NERVES OF AMPHIBIA. 119 



(^2 VII b^^ proceeds cephalad parallel to the main facial branch 

 and finally reunites with it (560), without having, apparently, 

 in the meanwhile, given off any fibres. 



The main subdivision of the dorsal VII (^VII b^ continues 

 cephalad along the dorsal surface of the head and inside the 

 eye to the extremity of the head. At intervals it gives off 

 twigs similar to those of the other subdivision; like them, 

 evidently supplying the line of lateral sense-organs in this 

 region. 



The parallelisms in courses between the trigeminal and facial 

 twigs above described are very striking, and are often observed 

 even in very minute ramifications. The significance of these 

 parallelisms will be discussed below. 



Somewhat more light is thrown upon the relations of these 

 trigeminal and facial branches by means of Golgi preparations. 

 The two facial branches, as they separate from the Gasserian 

 ganglion, seem to be composed exclusively of the coarse, heavily 

 medullated fibres so characteristic of them, nor do both, or even 

 one of them, always appear to receive directly a sympathetic 

 twig. 



The trigeminal branches, however, contain, besides the 

 medullated fibres of varying sizes as already noted, a number of 

 fibres which do not appear to b^ medullated and are impreg- 

 nated. These appear to have rather the character of nervi 

 nervorum and some of them, at least, though apparently not all, 

 can be traced to the sympathetic. When fusions take place 

 with the facial branches, though the integrity of the two 

 branches is in the main preserved, yet a number of these fine 

 fibres pass from the trigeminal to the facial twig and join the 

 latter. 



The ventral VII + Y^ the dorsal VII (VII aa + VII ab -\- y2 

 Vll b) consists, as above stated, of three components: one 

 (VII ab), the most ventral in derivation, from a motor nucleus 

 (or the posterior longitudinal fasciculus or both), one (VII ^^) 

 from the fasciculus communis and the third {% VII b) from the 

 ventral half of the dorsal VII which later joins the two former. 

 Where the first two components are fused with the VIII the 

 ventral root (VII ab) comes to occupy the outer position and 



