LI Electronmicroscopic Study of the Efferent and Afferent Innervation of the Organ of Corti in the Cat

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Abstract
In different groups of cats the homo- and contralateral olivocochlear bundle of one side, the cochlear nerve or the VIII nerve were cut. After a survival from ten days to four months, the animals were killed and brain stems and cochleas were examined under the light and electronmiscroscope. Together with the olivocochlear bundle the large vesiculated type of nerve endings in the organ of Corti degenerated, proving their efferent nature. The estimated number of efferent vesiculated nerve endings is a multiple of the fibers of the olivocochlear bundle; many ramifications must be assumed. The axons of the efferents cross the tunnel as the already known upper tunnel radial fibers, coursing freely in the fluid in the tunnel. The dendrites of the afferents with their small nonvesiculated nerve endings, however, mostly cross the tunnel near the basilar membrane. These afferent dendrites in the organ of Corti persisted independently of the rest of the neuron after degeneration of the myelinated processes and cell bodies in the spiral ganglion. A very important relationship between supporting cells in the organ of Corti and the afferent dendrites was assumed.