It has been observed frequently that inner ear trouble caused by the chronic inflammatorydiseases of the middle ear. The etiology has not been cleared but the extension of the inflammation by the destruction of the bone. Another possible route of spread of the disease is through the round and oval window which are located between the inner ear middle ear cavity. In the surgical treatment of the chronic otitis media, the condition of the round window has to be studied prior to the surgery disease how to diagnose any defect of round window for the purpose for the restoration of the hearing. For such purpose the permeability of round window was studied. One tenth cc of 10% cocaine hydrochloride was injected through the ear drum into the inner ear cavity of normal ear, middle ear disease and inner ear disease, and the symptons of autonomic nerve reaction was studied in conjunction with the change in the audiograph. Furthermore, various experimental hearing disordes were studied in the animals in order to endorse the results of the clinical experiments.The results of the investigations were as follows:The autonomic nerve reaction and subjective symptoms were obseeved in case with otosclerosis, sequela of otitis media, chronic otitia media with perforation, healthy ear, Meniere's syndrome and nerve deafness. In aminal experiment, symptoms appeared in conductive deafness (produced by cement injection), conductive deafness (otitis media), healythy ear, and perceptive deafness.The change on the audiograph:-In the cases with healthy ear and also perceptive deafness, the decrease in the thereshold both in air and bone conduction was observed below 2048 c.p.s and the increase in the threshold in air and bone conduction over 2048 c.p.s. In conductive deafnes due to inflammatory condition, the threshold was decreased below 3068 c.p.s in air and bone conduction. In those due to non-inflammatory condition, the change was minimal. Also, in case with remarkable autonomic nerve reaction, the increase of the threshold in higth tone, was observed. The tinnitus gave a certain influence to the audible threshold at the same frequency.Consequently, the cocaine solution being injected into the middle ear cavity may cause a certain trouble of inner ear passing through the round window. When there is a thickening of the membrane of round window such as in cases with chronic otitis media, in some cases the permeability is low and this must be kept in mind at the time of surgicol treatment. The condition of round window is clinically able to be evaluated by the injection of cocaine solution.