86 NERVE COMPONENTS OF BONY FISHES. 



The vagus group, as here defined, contains general 

 cutaneous, acustico-laterahs, communis and viscero-motor 

 components. The general cutaneous component is very 

 small, the acustico-lateralis and viscero-motor are of con- 

 siderable size, but the communis fibres make up by far 

 the larger portion of the complex. This latter system is, 

 however, far less highly developed here than in some 

 other teleosts, such as the cyprinoids, in which the vagal 

 lobes attain so enormous proportions. The IX nerve re- 

 ceives communis and viscero-motor fibres; the X nerve 

 proper receives communis, viscero-motor and general 

 cutaneous fibres. The n. lineae lateralis, conventionally 

 associated with the vagus, has no obvious morphological 

 relation to the other components of this complex. 



I. — The Roots and Ganglia of the Vagus Group. 



The roots of the IX and X nerves are quite widely sepa- 

 rated, the former arising under the origin of the r. lateralis 

 vagi. The sensory and motor roots of the IX nerve are 

 distinct at their origins, though close together, and they 

 unite immediately after leaving the brain. The various 

 elements of the vagus (aside from the r. lateralis) are so 

 intimately united that analysis by gross methods would 

 be quite impossible. 



/. — TJie Communis Root of tJie N. Glossopharyngeiis. 



The sensory root of the IX nerve emerges from the 

 brain just dorsally of the motor IX and these two roots 

 diverge from each other very rapidly in passing toward 

 their respective centres. The communis root passes dor- 

 sally of the spinal V tract, the motor root ventrally of it. 

 This sensory root runs directly inward as a close round 

 bundle of very fine fibres until it reaches the fasciculus 



