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Interior of the ear. There is external to the head a wide-mouthed tube, or ear-trumpet (a), for catching and concentrating the waves of sound. It is movable in many beings, so that they can direct it to the place from which the sound comes. The sound concentrated at the bottom of the ear-tube falls upon a membrane stretched across the channel, like the parchment of an ordinary drum, over the space called the <em>tympanum</em>, or <em>drum of the ear</em> (b), and causes the membrane to vibrate. That its motion may be free, the air contained within the drum has free communication with the external air by the open passage (f), called the <em>eustachian tube</em>, leading to the back of the mouth. A degree of deafness ensues when this tube is obstructed, as in a cold; and a crack, or sudden noise, with immediate return of natural hearing, is, generally experienced when, in the effort of sneezing or otherwise, the obstruction is removed. The vibrations of the membrane of the drum are conveyed further inwards, through the cavity of the drum, by a chain of four bones (not here represented on account of their minuteness), reaching from the centre of the membrane to the <em>oval door</em> or <em>window</em>, leading into the labyrinth (e). The labyrinth, or complex inner compartment of the ear, over which the nerve of hearing is spread as a lining, is full of watery fluid; and, therefore, by the law of fluid pressure, when the force of the moving membrane of the drum, acting through the chain of bones, is made to compress the water, the pressure is felt instantly over the whole cavity. The labyrinth consists of the <em>vestibule</em> (e), the three <em>semicircular canals</em> (c), imbedded in the hard bone, and a winding cavity, called the <em>cochlea</em> (d), like that of a snail-shell, in which fibres, stretched across like harp-strings, constitute the <em>lyra</em>.

Ear

Interior of the ear. There is external to the head a wide-mouthed tube, or ear-trumpet (a), for catching…

A view of the labyrinth laid open. Labels: 1, The cochlea. 2, 3, Two channels that wind two and half turns around a central point (5). 7, The central portion of the labyrinth called the vestibule. 11, 12, 13, 14, 15, 16, 17, 18, The semicircular canals.

View of the Labyrinth Laid Open

A view of the labyrinth laid open. Labels: 1, The cochlea. 2, 3, Two channels that wind two and half…

Diagrammatic representation of the different parts of the membranous labyrinth.

Labyrinth

Diagrammatic representation of the different parts of the membranous labyrinth.

Membranous labyrinth of a five months' fetus, viewed from its postero-mesial aspect.

Labyrinth of Fetus

Membranous labyrinth of a five months' fetus, viewed from its postero-mesial aspect.

View of the labyrinth in a straight position, open to show the distribution of the nerves.

Labyrinth of the Ear

View of the labyrinth in a straight position, open to show the distribution of the nerves.

View of labyrinth on the left side, open throughout, in order to show its structure -- enlarged.

Labyrinth of the Ear on the Left Side

View of labyrinth on the left side, open throughout, in order to show its structure -- enlarged.

The labyrinth of the middle ear, which is composed of a system of fluid passages.

The Labyrinth of the Inner Ear

The labyrinth of the middle ear, which is composed of a system of fluid passages.

A view of the labyrinth of the left side laid open in its whole extend, so as to show its structure - magnified.

The Labyrinth of the Inner Ear

A view of the labyrinth of the left side laid open in its whole extend, so as to show its structure…

A highly magnified view of the external face of the bony labyrinth of the left side, opened so as to expose the vestibule and its contents, etc.

Bony Labyrinth of the Inner Ear

A highly magnified view of the external face of the bony labyrinth of the left side, opened so as to…

A, Left labyrinth of a human embryo of about four weeks; B, left labyrinth of a human embryo of about 5 weeks.

Development of Labyrinth

A, Left labyrinth of a human embryo of about four weeks; B, left labyrinth of a human embryo of about…

View of the interior of the left labyrinth. The bony wall of the labyrinth is removed superiorly and externally. Labels: 1, fovea hemielliptica; 2m fovea hemispherica; 3, common opening of the superior and posterior semicircular canals; 4, opening of the aqueduct of the vestibule; 5, the superior, 6, the posterior, and 7, the external semicircular canals; 8, spiral tube of the cochlea (scala tympani); 9, opening of the aqueduct of the cochlea; 10, placed on the lamina spiralis in the scala vestibuli.

Interior of the Left Labyrinth

View of the interior of the left labyrinth. The bony wall of the labyrinth is removed superiorly and…

Left bony labyrinth viewed from outer aspect.

Outer Aspect of Labyrinth

Left bony labyrinth viewed from outer aspect.

Interior of left bony labyrinth viewed from outer aspect.

Outer Aspect of Interior Labyrinth

Interior of left bony labyrinth viewed from outer aspect.

A medal of Crete, representing a Minotaur and the labyrinth in which he was confined.

Medal of Crete

A medal of Crete, representing a Minotaur and the labyrinth in which he was confined.

Diagram to illustrate the action of the ossicles of the middle ear in the conduction of sound to the internal ear.

Ossicles of the Middle Ear

Diagram to illustrate the action of the ossicles of the middle ear in the conduction of sound to the…