METHOD

Seventy-three mice in 17 litters of the CBA-J strain were used. Each animal was compared with a litter mate. This was done to reduce the variation which was found between mice from different litters (Fig. 1). The mice were anesthetized with intraperitoneal urethane. The bulla was exposed, being careful not to destroy the horizontal semicircular canal or the stapedial artery. The VIII nerve was exposed by placing a small hole in the calvarium and aspirating a portion of the cerebellum. A Zeiss operating microscope was used for all operative procedures.

The electrode for the round window membrane recordings consisted of a platinum wire 0.003" in diameter insulated with teflon. Recordings from the round window membrane in the adult animal were made with a ball tip electrode. A plain tip was used to record from the round window membrane in the developing mouse. The plain tip was also used to record from the VIII nerve in all animals. The active electrode was recorded with respect to an indifferent electrode placed in the muscles of the neck. A ground was placed either on the back or attached to the tail.