EXPERIMENTAL STUDIES ON THE MECHANISM OF SOUND CONDUCTION OF THE OSSICULAR CHAIN THROUGH ITS PARTIAL RESECTION

Abstract

In order to make clear the mechanism of sound conduction of the ossicular chain, the author investigated the alteration of response of the cochlear microphonics through the partial resection of the malleus, the stapes or both of them of many cats at several different points.The results were summarized as follows:(A) After cutting the malleus at either the middle portion of the manubrium or the short process, there appeared little reduction of response of the cochlear microphonics.The losses were about 5_??_15db in the range from 0.25 to 8kcps.(B) After cutting the malleus at both the short process and the manubrium, the losses grew more remarkable at high frequencies, and it was about 40db at 8kcps on the average of 20 ears.(C) The cut through of the tendon of tensor tympani muscle gave only a very slight additional loss of response at high frequencies.(D) After cutting the tendon of stapedius muscle and the malleus at the lateral ligament, there were little changes in the response of the cochlear microphonics.E) After cutting the stapes at either the anterior crus or the posterior, the loss of response was 17 to 18db at 8kcps.(F) After cutting either the malleus at the neck or the stapes at both the anterior crus and the posterior, the loss of response was about 50 to 60db in the range from 0.25 to 8kcps.(G) After cutting the stapes at either the anterior crus or the posterior, the author cut the malleus at the middle portion of the manubrium.There appeared the additional effect of each loss of response.(H) From the above data it is presumed that the contraposition of the navel of the manubrium of the malleus and the short process or the anterior crus and the posterior of the stapes has a special effect for the high tone conduction.