Some new aspects on damages in the organ of Corti after pure tone exposure.

(1) The loss of hair cells after pure tone exposure at the critical level of intensity shows an exact correlation to the frequency, the time of sound exposure, and time of recovery as regards the quality and quantity. (2) The total extent of the damage of sensory cells has to be estimated higher than the hair-cell loss as observed under the light microscope. Although an improvement of the function of the organ of Corti was determined electrophysiologically from the 5th to the 10th day of recovery, the hair-cell degeneration was progredient during this period. (3) The hair-cell damage is apically more strongly marked from the area of damage than basically. (4) Depending on the experimental conditions there are considerable degenerative alterations in the nerve fibres and in the connective apparatus of the organ of Corti besides hair-cell losses and damages.