REVIEW OF THE CRANIAL COMPONENTS. 273 



2. — The Aciistico-lateral System. 



These nerves are related exclusively to the organs of 

 the lateral line canals and allied sense organs, and to the 

 similar organs of the internal ear. The system includes 

 the ganglion of the acustic nerve, the ganglion of the r. 

 lateralis vagi and the dorsal and ventral lateralis ganglia 

 of the facialis, together v^ith their root fibres and their 

 common terminal nuclei in the tuberculum acusticum and 

 cerebellum. Most of these root fibres terminate soon 

 after their entrance into the brain in the tuberculum 

 acusticum, but some turn cephalad to terminate in the 

 cerebellum, while others turn as abruptly caudad to form 

 a spinal VIII tract. 



This system has no representative in the spinal nerves. 

 The extreme dorsolateral position of its terminal nucleus 

 and of the ascending and descending root bundles suggests 

 that this system was the last sensor>^ system to be differ- 

 entiated in the medulla oblongata. It is closely related to 

 the general cutaneous system ; nevertheless from a study 

 of Weigert preparations of Menidia I cannot agree with 

 Johnston ('98), who finds from a study of Golgi prepara- 

 tions of Acipenser that the acustico-lateral and the general 

 cutaneous nerves belong to a single system with a com- 

 mon terminal centre in the oblongata. The two systems 

 are very distinct from each other in Menidia both 

 centrally and peripherally. It is possible that the 

 acustico-lateral system has been derived in the phy- 

 logeny from the general cutaneous, a view which has 

 been expressed by Cole ('97, p. 234) on embryological 

 grounds. 



See Section 2; Section 3, II; Section 5, I, 5 and X; 

 Section 6; and Section 7. 



