822 



DISSECTION OF THE EAR. 



cochlear 

 nerve has a 

 spiral 

 ganglion, 



and ends in 

 organ of 

 Corti. 



Vessels of 

 labyrinth. 



Auditory 

 artery from 

 basilar, 

 has a 



vestibular, 



and a 

 cochlear 

 branch . 



Veins to 

 petrosal 

 sinuses and 

 internal 

 jugular. 



The cochlear nerves traverse the canals of the modiolus, and; 

 bend outwards in the passages of the lamina spiralis (fig. 304, 2 ). 

 As they enter the latter, they join a ganglion (ganglion spirale) 

 which occupies a winding canal at the junction of the lamina 

 spiralis with the modiolus ; and from this they are continued as 

 fine branches, forming a close plexus, to the organ of Corti. 



BLOOD VESSELS. The membranes of the labyrinth are supplied 

 by an artery which enters the internal auditory meatus with the 

 auditory nerve. The veins are more numerous. 



The INTERNAL AUDITORY ARTERY arises from the basilar trunk 

 within the skull, and divides in the internal auditory meatus 

 into two branches, one for the vestibule, and the other for the 

 cochlea. 



The vestibular artery subdivides into small offsets which enter the 

 cavity with the branches of the auditory nerve, and ramify over the 

 sacs and the semicircular canals. 



The cochlear branch breaks up into numerous fine twigs which 

 enter the modiolus and the canals in the lamina spiralis. Offsets 

 supply the nerve and the parts in the neighbourhood of the limlms 

 laminae spiralis, and others ramify in the periosteal lining of the 

 scalse ; but there are no vessels in the outer part of the membrana 

 basilaris. 



VEINS. The internal auditory vein accompanies the artery, and 

 ends in the inferior petrosal sinus in the base of the skull. The 

 vein of the aqueduct of the cochlea joins the internal jugular ; and the 

 vein of the aqueduct of the vestibule opens into the superior petrosal 

 sinus. 



