The long-term objective of this study is to investigate the ultrastructure of normal animal inner ears as well as experimentally induced pathological ears for the purpose of increasing our knowledge on the working mechanisms of the auditory and vestibular systems. The main focus of the animal experiments is directed toward the identification of the etiology and the treatment of Meniere's disease. The specific aims are: 1) aided by an integrated computer system, to conduct a morphometrical study on the membranous wall of the cochlear duct and fluid spaces using serial sections for light microscopy, and on the outer and inner hair cells, stria vascularis and cell organelles using serial sections for electron microscopy; 2) to conduct morphological studies on the cochlear nerve fibers by studying serial sections, and autonomic nerve fibers by injection of horseradish peroxidase and histochemical techniques; 3) to conduct a tracer study to test the theory of longitudinal flow of endolymph from the vestibular labyrinth into the endolymphatic sac, and to determine if perilymph flows or moves in either the apical or basal direction in the cochlear; 4) to perform experimental studies on endolymphatic hydrops related to Meniere's disease. An attempt will be made to create a better animal model which will demonstrate endolymphatic hydrops associated with dizziness using a less invasive method. Furthermore, major emphasis will be placed on the control of endolymphatic hydrops in the existing animal model by applying various drugs based on different actions.