1150 



THE ORGANS OF SPECIAL SENSE 



of the floor of the meatus. It also gives off the branch for the ampulla of the pos- 

 terior semicircular canal, which leaves the meatus through the foramen singulars. 

 The rest of the cochlear nerve divides into numerous filaments at the base 

 of the modiolus; those for the basal and middle coils pass through the foramina 

 in the tractus foraminosus, those for the apical coil through the canalis centralis, 

 and the nerves bend outward to pass between the lamellae of the osseous spiral 

 lamina. Occupying the spiral canal of the modiolus is the spiral ganglion, or 

 ganglion of Corti (ganglion spirale}, consisting of bipolar nerve cells, which really 

 constitute the true cells of origin of this nerve, one pole being prolonged centrally 

 to the brain and the other peripherally to the hair cells of Corti's organ. Reaching 

 the outer edge of the osseous spiral lamina, the nerve fibres pass through the foram- 

 ina in the labium tympanicum. Some of these fibres end by arborizing- around 

 the bases of the inner hair cells, while others pass between Corti's rods and across 

 the tunnel, to terminate in a similar manner in relation to the outer hair cells. 



The arteries of the labyrinth are the internal auditory, from the basilar, and the stylomas- 

 toid, from the posterior auricular. The internal auditory divides at the bottom of the internal 

 auditory meatus into two branches, cochlear and vestibular. The cochlear artery divides into 

 numerous minute branches, which enter foramina in the tractus spiralis foraminosa and course 

 in the lamina spiralis ossea to reach the membranous structures. The largest of the cochlear 

 branches is in the canalis centralis. The vestibular branches accompany the nerves, and sup- 

 ply the membranous structures in the vestibule and semicircular canals. Two arteries go to each 

 canal. The two vessels enter opposite extremities of the canal, and anastomose at the summit 

 of the canal. The vestibular vessels form a minute capillary network in the substance of each 

 membranous labyrinth. 



The veins of the vestibule and semicircular canals, the auditory veins, accompany the 

 arteries, and receive those of the cochlea at the base of the modiolus, to form the internal 

 auditory vein (w. auditivae internae), which opens into the posterior part of the inferior petrosal 

 sinus or into the lateral sinus. 



THE ORGANS OP TASTE (ORGANON GUSTUS). 



The peripheral organs of the sense of taste consist of certain flask-shaped 

 groups of modified epithelial cells, termed taste buds (calyculi gustatorii), situated 

 on the tongue and adjacent parts. They occupy nests in the stratified epithelium 



Papillce 



Taste- 

 buds 



FIG. 859. Section of part of the papilla foliata of a rabbit. (Magnified.) 



and are present in large numbers on the sides of the circumvallate papillae (Fig. 

 859), and to a less extent on their opposed walls. They are also found on the 

 fungiform papillae over the back part and sides of the tongue, and in the general 



