AND PHYSIOLOGY. 



393 



lymph and nerve fiber, which take the general direction of a 

 semicircle. Of these cavities, however, the cochlea is not 

 filled with the perilymph, but contains the finest subdivisions 

 of the auditory nerve. Besides the cochlea and semicircular 

 canals there is a small three-cornered cavity called the Vesti- 

 bule, into which the five openings of the semicircular canals 

 enter. 



718. Auditory Nerve.— The nerve of hearing; belongs to 

 the eighth pair of Cranial nerves. It divides into two 

 branches just before it enters the ear, one of which is called 

 the cochlear branch, because it is sent to the cochlea, and an- 



Fig. 364. 



Auditory Nerve taken out of the Cochlea. 1, 1, 1, Trunk of the Nerve. 2, 2, Its fila- 

 ments in the Zona Ossea of the Lamina Spiralis. 3, 3, Its Anastomoses in the Zona Vesi- 

 cularis. 



other the vestibular, since it enters the vestibule, a portion of 

 the labyrinth. Besides this a branch of the facial nerve en- 

 ters the ear in company with the auditory. 



719. Location of the Internal Ear.— In man and all 

 the higher animals there are two separate organs of hearing, 



Describe the cochlea. What are the semicircular canals? What are they filled with? 

 T18. What is the nerve of hearing ? 719. In what bone is the ear located ? 



