COCHLEA. 389 



are slender bodies each containing a stiff filament. They have a cap- 

 like cuticular border so that they remotely resemble the distal phalanges 

 of the fingers. The spaces between the "phalanges" are occupied by the 

 outer hair cells. The cuticular expansions connect with one another 

 forming a reticular membrane, into the apertures of which the hair cell 

 processes extend. The sustentacular cells resemble the pillar cells, but 

 their transformation into stiff fibers has not proceeded so far; the cutic- 

 ular border is comparable with the head plate. The most peripheral of 

 the sustentacular cells are followed by elongated columnar cells (cells of 

 Hensen) which gradually shorten and pass into the undifferentiated epi- 

 thelium of the cochlear duct. The low cells following Hensen's cells are 

 the cells of Claudius. They are said to have branching bases which extend 

 deep into the underlying tissue. In both the columnar and the low forms 

 there are single stiff filaments which are less developed than in the susten- 

 tacular cells. The centrosomes of all these cells lie near their free surfaces. 



NERVES AND VESSELS OF THE LABYRINTH. 



The acoustic nerve is a purely sensory nerve passing between the pons 

 and internal ear through a bony canal, the internal auditory meatus. It is 

 divided into vestibular and cochlear portions (Fig. 432). The vestibular 

 nerve proceeds from the vestibular ganglion and has four branches; the 

 utricular nerve and the superior, lateral, and posterior ampullary nerves. 

 Their terminations have already been described (p. 384). The cochlear 

 nerve, which has a saccular branch, proceeds from the spiral ganglion 

 lodged within the modiolus at the root of the lamina spiralis (Figs. 432 and 

 435). The ganglion cells remain bipolar like those of embryonic spinal 

 ganglia. The neuraxon and the single peripheral dendrite are medullated 

 except near the cell body. The peripheral fibers extend through the lamina 

 spiralis ossea, within which they form a wide meshed plexus, and after 

 losing their myelin they emerge from its free border through the foramina 

 nervosa. In continuing to the spiral organ they curve in the direction of 

 the cochlear windings, thus producing spiral strands. Those nearest the 

 modiolus are on the axial side of the pillar cells; the middle ones are between 

 the pillars, in the tunnel; and the outer ones are beyond the pillar cells. 

 From these bundles delicate fibers pass to the hair cells, on the sides of 

 which they terminate. 



The internal auditory artery is a branch of the basilar artery. It 

 arises in connection with branches which are distributed to the under 

 side of the cerebellum and the neighboring cerebral nerves, and passes 

 through the internal auditory meatus to the ear. It divides into vestibular 

 and cochlear branches. The vestibular artery supplies the vestibular nerve 



