■62 HUMAN EMBRYOLOGY AND MORPHOLOGY. 



By uncertain tracts the central auditory terminations in the 

 medulla are connected with : — 



(1) The cerebellum ; 



(2) The superior olive ; 



(3) The posterior corpora quadrigemina ; 



(4) The middle third of the 1st temporal convolution in 

 which is situated the "word-hearing" centre (Fig. 46). 



Internal Auditory Meatus. — The internal auditory meatus is 

 formed round the Vlllth nerve, its ganglia, and the Vllth nerve. 

 The falciform crest separates the fibres of the lateral from the 

 fibres of the mesial root. The meatus also contains a prolonga- 

 tion of the arachnoid and subarchnoid space. Fractures of the 

 base of the skull frequently cross the petro-mastoid in the line of 

 the internal auditory meatus, vestibule and membrana tympani. 

 In such cases the cerebro-spinal fluid and perilymph may escape 

 by the external auditory meatus. 



