Nerve fibers in the fetal organ of Corti. Scanning electron microscopic study.

Four human fetal inner ears ranging from 22 to 25 weeks' gestation were examined by scanning electron microscopy. Dissection of the organ of Corti revealed nerve fibers at the bottom of Corti's tunnel and the first row of the external spiral bundles on the medial wall of Deiters' cells. The nerve fiber arrangement was more complicated compared to that of animals so far reported. Thin nerve fibers which ran irregularly and showed branching were found both in Corti's tunnel and in the external spiral bundle and at times were connected to the tunnel medial fibers. These thin fibers were estimated to be efferent in nature.