414 Journal of Comparative Neurology. 



neous fibres. These now arise from the Gasserian gan- 

 g-lion and we should have to assume that their ganglion and 

 root have secondarily fused with the trigeminal, as the 

 profundus ganglion is supposed to have done. 



The trigeminus segment has suffered still greater modi- 

 fication. The root contains no communis fibres, for there 

 is no vertebrate known in which there is a pre-facial fas- 

 ciculus communis. The post-trematic ramus, i. e.^ the r. 

 mandibularis V, has viscero-motor and general cutaneous 

 fibres, and, as we have just seen, communis fibres belong- 

 ing to the pre-trematic VII may secondarily be distributed 

 peripherally with this ramus. 



The pre-trematic ramus, or r. maxillaris, has typically 

 only general cutaneous fibres. In some, perhaps most, 

 fishes there are joined to these also some communis 

 fibres from the geniculate ganglion for taste buds about 

 the upper lip, but these are not proper trigeminal 

 fibres. 



The absence of a pre-facial fasciculus communis and 

 communis root of the trigeminus involves the lack of a 

 r. palatinus for this segment. Functionally this is re- 

 placed by the forward extension of the r. palatinus VII. 



The r. ophthalmicus superficialis V may represent a 

 dorsal branch of typical form, to which communis fibres 

 are added in some types for terminal buds on the top of 

 the head and to which the lateralis fibres of the r. 

 ophthalmicus superficialis VII may also be joined. 

 The r. ophthalmicus profundus might possibly rep- 

 resent a lateral ramus of this segment, though more 

 probably it belonged originally to a segment lying farther 

 cephalad and is only secondarily joined to the trigeminus 

 segment. 



