Animal experiments on the mechanism of the acoustic irritation in the cochlea

Abstract

AbstractExperiments† have been performed which aim to throw light upon the mechanism by which the nerve endings in Corti's organ are stimulated. The physiological stimulus of the cochlea consists in dynamic air pressure changes which are transformed into vibrations of the intralabyrinthine fluid. Since static pressure changes are easier to analyze, they were studied first. The displacement of the intralabyrinthine fluid due to static pressure changes in the outer acoustic canal and in the middle ear cavity was measured by the following method:A tube was inserted into the outer acoustic meatus of a rabbit and made airtight. A second tube was fixed into the middle ear, and this opening was also firmly closed. Both tubes were connected with a syringe in which changes in pressure could be produced. A second connection was made with a manometer, by means of which the pressures were measured. The inner ear of the animal was opened and a tiny glass capillary was inserted. By an optical system the meniscus was visualized on a screen; movements of the meniscus due to changes in pressure in either the middle or the outer ear could be observed fairly accurately (see Fig. 1).