Abstract
An enormous amount of research has been reported on the acoustic trauma since the experimental study of this trauma was initiated approximately half a century ago. However, some of its pathogenesis, course and general characteristics have not been clearly elucidated as yet. The reversibility of the acoustic trauma is one of the problems still remain unsolved. In the present experiment, the acoustic trauma of Corti's organ of guinea pigs was induced by exposin g the animals to a white noise of 115 phons, 8 hours per day, for a few days. The traumatized inner ears of guinea pigs without receiving any treatment has been daily observed in comparison with those of the animals treated with various drugs. By this mean the author intended to throw some light on the susceptibility of the guinea pig's inner ear to the acoustic trauma and the reversibility of the traumatic changes being so induced. The results obtained will be summarized as follows:
1. No recognizable change appeared in the Corti's organ of guinea pigs exposed to the noise for one day, while the exposure for 3 days resulted in a definite change. This is apparently due to the resistivity of the animal's organ against the acoustic load.
2. The acoustic trauma induced in this way could be divided into two types showing different courses. In one type (A), the traumatic change was fixative or showed a slight improve ment as the time advanced. Namely, the resulted change did not progress further and was somewhat reversible. On the other hand, in the other type (B), the traumatic change was progressive and Corti's organ usually showed a marked atrophy or sometimes it disappeared eventually.
3. Drugs given to the guinea pigs showing the type A change accelerate the healing of the pathological changes of the inner ear, while those given to those of type B slightly retarded the progress of the degenerative change or had no effect at all.
4. Traumatic changes of the inner ear showed a conside rable difference from animal to animal in spite of the acoustic load was given under the same condition. It would be extremely difficult to investigate the cause, but the diversity may be regarded as the individual d ifference in the intrinsic facter of each animal.
