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Updated: May 26, 2025
For the latter kind of transmission it is necessary that the pressure on both sides of the drum-membrane should be equal, and this is arranged by the admission of air to the middle ear through a passage from the throat.
The office of these tubes is to supply air to the cavity on the inner side of the drum-membrane, known as the middle ear. As is well known, a passage exists from the outer ear to the drum. The Eustachian tubes connect the middle ear with the upper portion of the throat from whence the air supply to the middle ear is obtained.
With the closure of the Eustachian tubes the air supply to the middle ear was cut off; the air in the cavity finally became absorbed, and a retraction and thickening of the drum-membrane with consequent inability to transmit sound vibrations followed.
But even in the absence of a drum-membrane an adult can hear; the vibrations in such cases are transmitted through the bones of the skull, and this very likely also occurs in newly born infants. In most instances, at least, they react to a disagreeable noise within the first twenty-four hours, and their sensitiveness in this direction explains why the nursery should be kept quiet.
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