470 THE INTERNAL STRUCTURE 



cross over to the opposite side, and go to form part of the 

 sensory tract or ' tegmentum ' of the opposite Cerebral 

 Peduncle (see p. 478). 



The Auditory Nerve enters the side of the Medulla just 

 below the ' pons ' :n close relation with the root of the 

 Facial Nerve. A'bout the subsequent very complicated 

 course of its fibres we still have much to learn. A large 

 section of them, at least, seem to enter the Cerebellum, 

 and the mode by which the opposite Cerebral Hemisphere 

 is brought into relation with its fibres and nuclei of origin 

 is altogether obscure. Mej^nert even says :* " We may 

 regard it as certain that no extensive immediate connection 

 of the auditory nerve with the Cerebral lobes exists, but 

 that such a connection, the existence of which may be 

 assumed as a necessary physiological truth, can only come 

 to pass indirectly through the Cerebellum." 



How far this view of Meynert's is absolutely correct 

 cannot at present be determined. We do know, however, 

 from evidence which will be subsequently referred to in 

 regard to Hemi-ansesthesia (p. 487), that a decussation 

 of auditory channels takes place, and that these channels 

 ultimately become incorporated with other fibres of the 

 Cerebral Peduncles comprised within the posterior third 

 of what is known as the ' internal capsule.' 



It must, moreover, not be forgotten that, according to 

 Cyon (p. 218), what is named by him as the Space-nerve 

 (Eaumnerv) is also bound up with, and forms part of the 

 trunk commonly known as the ' Auditory/ The internal 

 course of the portions belonging to each of these nerves 

 will, if this view be correct, have to be subsequently 

 determined and differentiated. It may be that it is the 

 fibres of this Space-nerve more especially which come 

 into immediate relations with the Cerebellum (see p. 506). 

 * Strieker's Histology, vol. ii. p. 500. 



