Nerve fibers in the human organ of Corti.

In the human cochlea, the following characteristics of nerve fiber arrangements were observed. 1. Where there was only the basilar fiber in the tunnel of Corti, the internal and tunnel spiral bundle were not observed. In such cases, the number of nerve fibers in the external spiral bundle was small. 2. In the tunnel of Corti, the basilar fibers (afferent) took a course at the base and crossing the tunnel slanting to the basal end. 3. The medial fibers were present with the internal spiral bundle and tunnel spiral bundle. These fibers are possibly efferent. 4. The external spiral bundle increases its fiber count when internal and tunnel spiral bundles were present in the organ of Corti. 5. The external spiral bundle was composed of the basilar and medial fibers. The former were less and the latter much more numerous in the bundle. 6. 85-90% of the afferent fibers went to the internal hair cells, while the remainder went to the external hair cells. 7. The nerve fibers were found in the organ of Corti lateral to the external spiral bundles. The fibers were running in the Hensen's and Claudius' cell area. 8. In some cases medial fibers showed a torpedo-like deformity in the tunnel of Corti. When this was observed, it was found distributed throughout the entire cochlea. Hearing disorders due to this pathology of the efferent fiber was suggested.