Investigations were made on the retation of the hearing and the disturbances of the con-ductive system in chronic infection of the middle ear, and the following results were obtained
1. In chronic infection of the middle ear, disturbances of the inner ear and absence of mobilization of the stapes account greatly for the loss of air conduction, and in cases of severe impairment of air conduction, the threshold of bone conduction was frequently enhanced. In the cases with impaired mobilization of the stapes, the loss of air conduction more than 50 db was noted in all cases, being more than 60db in most of the cases.
2. When the factors contributing to disturbance of inner ear were removed, the hearing thresholds were between 30 and 50 db in the cases whose ossicles were intact. There was no specific relationship between the size of the perforation of the ear drum and the loss of air conduction, but there was a tendency of greater impairment in hearing when the perforation of the drum was located in the upper posterior quadrant. The cases in which the ossicular chain was separated showed thresholds of 40_??_60 db. Cases with the mild caries of the ossicles without impairment of chain function showed the loss similar to that of the case with intact ossicles.
3. In chronic infection of the middle ear, the frequency characteristic showed largest im-pairment in the range of low to middle sounds, especially in the low tone zone.
Report 2. Test for changes in the ossicles by means of the sound probe
An attempt was made to examine the state of the ossicle by measuring the threshold of sound conduction by the ossicular chain by means of the sound probe. There was a clear diffe-rence in the thresholds between those with intact or mild caries of the ossicles but with retai-ned the ossicular chain function, and those with separated ossicular chain separated or with loss of mobilization of the stapes. Thus it may be stated that the sound probe can be used for evoluation of the ossicular function.
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