Abstract
The experiments were performed on several living cats, in whose middle ear cavities the negative air pressure was caused by means of drawing the air directly out, pressing it into the external auditory meatus, or simultaneously giving the equal negative pressure into the external auditory meatus and the middle ear cavity.The results were as follows:(1) The decreasement of the air pressure in the middle ear cavity caused by drawing the air directly out as well as pressing it into the external auditory meatus reduced evidently the cochlear electric response, and generally low tones showed clearer effects than high tones.(2) On these experiments, some enhancement of the response was recognized at 2000, 4000, and 8000cps by certain valus of the negative pressure.(3) There was no distinct difference between the effects of the negative air pressure in the middle ear cavity and that caused by the positive air pressure in the external auditory meatus.(4) At the negative pressure of 4cm height of mercury given simultaneously in the external auditory meatus and the middle ear cavity, the decreasement of the cochlear electric response was generally about 2db.(5) Therefore the influence of the negative pressure in the middle ear cavity upon the hearing ability is considered mainly on the transmission system of the drum membrane and the ossicular chain.
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