THE CRANIAL NEKVES AND LATERAL SENSE ORGANS OF FISHES. 177 



The above consideration of the literature and description of the facts ia Gadiis 

 enable us to draw u^i the following general conclusions as to the structure and 

 morphology of the accessory lateral nerves : — 



(1) The accessory lateral system of nerves is essentially compound in nature, the 



anterior branches as they pass backAviirds acting as collectors and picking up 

 branches from nerves situated posterior to them. 



(2) The systera therefore belongs as distinctively to the spinal as to the cranial 



nerves. It originates in the latter, passes backAvards, and collects branches 

 from the former. 



(3) It is distributed to the fins — typically, as in Gadns, to all the fins of the body, but 



in some fishes it may l)e di8tril)utpd to only one or more of the fins. 



(4) In connection M'ith the fins are a number of tei'minal buds or Eiidknospeii, a)ul 



the fibres of the accessory lateral system are largely, if not entirely, in 

 connection -with these sense organs. The system is therefore both essentially 

 somatic and sensory in function. 



(5) Hence we cannot escape the conclusion that it is formed by the dorsal branches 



of the cranial and spinal nerves which the exigencies of their distribution liave 

 caused to more or less fuse together peripherally. 



(6) Fvirther, the ganglion on the posterior or vagal root in Gadns is comparable to the 



somatic sensory j^ortion of the dorsal root ganglion of a spinal nerve. This 

 ganglion (and it is possible thei'e are otiiers) belongs distinctively to the accessory 

 lateral system. 



(7) The system in any one fish may be formed either liy the whole or portions of the 



dorsal somatic sensory branches of tlie trigeminal, facial, glossopharyngeal, 

 and vagal cranial nerves, together with the whole or portions of the dorsal 

 somatic sensory branches of a varia])le number of spinal nerves. 



(8) Upon no grounds caii it be considered as belonging to the lateral line series of 



nerves, since it differs irom the latter in three essential respects : (a) in internal 

 origin; (b) in the character of its fibres ; and (c) in its peripheral distribution. 

 The one system acts as a collector, whilst the other is absolutely independent of 

 any of the cranial or spinal nerves. 



(9) It is hence imperative to sink such ti'rms as " ramus lateralis trigemini," " ramus 



cutaneus quinti," and " ramus recurrens facialis," since no term can Ije 

 considered satisfactory, or indeed justifiable, which implies that any one cranial 

 or spinal nerve either invariably takes a part in, or entirely forms, this 

 complicated system of nerves. I have tidopted the term " Ramus lateralis 

 aceessorius " for three reasons: (1) it implies nothing as to the formation and 

 origin of the system ; (2) it was the first term to be apj^lied to these nerves ; 

 (3) its meaning that it is an accessory lateral nerve is one that may fitly be 

 applied to it, and is not ambiguous, since the term " lateralis " has been 

 indifferently applied both to special and general cutaneous nerves *. 



* Hence m}- term " lateralis lateral line la-rvo," which leaves no room for doubt as to its distributioji. 



