Observation of the Inner Ear in the Fetal Japanese Monkey (Macaca Fuscata)

Abstract

Morphology of the inner ear in a four-month fetus of Japanese monkey was observed by SEM and the following conclusions were obtained as a result. 1) The organ of Corti had three and a half turns and it was considered that the organ of Corti maturates about four months after gestation from the feature of sensory hairs and third row of Deiters' cells. 2) On undersurface of tectorial membrane, though the imprint of sensory hairs showed a spotted single row in the part of bilateral edge, it showed two or three rows in the central part. 3) In nerve fibers running on the bottom of the tunnel of Corti, there were two kinds of fibers those were quite different in the diameter and the way of running. 4) Sensory hairs of vestibular organs were mature enough and the absorption of otoconia was recognized on the dark cell area in utricle.