SENSE OF HEARING 



895 



and others have represented them as terminating in free loops, yet more care- 

 ful observation has rendered this doubtful ; and the general analogy between 

 the simpler forms of the auditory and of the visual apparatus, as well as the 



Fig. 217. 



General view of the external, middle, and internal Ear, as seen in a prepared section through a, the auditory 

 canal, b. The tympanum or middle ear. c. Eustachian tube, leading to the pharynx, d. Cochlea; and e- 

 Semicircular canals and vestibule, seen on their exterior, as brought into view by dissecting away the sur- 

 rounding petrous bone. The styloid process projects below; and the inner surface of the carotid canal is seen 

 above the Eustachian tube. From Scarpa. 



close correspondence which exists between them in the history of their develop- 

 ment (the organ of hearing, like the eye, being budded off from its sensory gan- 

 glion), seems to indicate that the peripheral expansion of the auditory nerve might 



Fig. 218. 



The Auditory Nerve taken out of the Cochlea : 1, 1, 1, the trunk of the nerve ; 2, 2, Its filaments In the zona 

 v ossea of the lamina spiralis ; 3, 3, its anastomoses in the zona vesicularis. 



be expected to have a structure analogous to that of the retina. The most exact 

 observations yet made on this point seem to be those of the Marquis Corti on 



