Investigates the occurrence of long-term recovery of mature hair bundle (MHB) numbers following gentamicin-induced damaged to the mammalian vestibular sensory epithelium. Decline of the MHB density; Comparison of lost numbers between type I and II MHB; Increase in immature hair bundle density; Absence of mammalian vestibular sensory epithelium for long term recovery of MHB numbers after gentamicin damaged.