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In time of battle soldiers sometimes have their tympanums ruptured by the concussion caused by the firing of cannon. Dalby mentions an instance of an officer who was discharged for deafness acquired in this manner during the Crimean War. He was standing beside a mortar which, unexpectedly to him, was fired, causing rupture of the tympanic membrane, followed by hemorrhage from the ear.
This face had no nostrils indeed, the Martians do not seem to have had any sense of smell, but it had a pair of very large dark-coloured eyes, and just beneath this a kind of fleshy beak. In the back of this head or body I scarcely know how to speak of it was the single tight tympanic surface, since known to be anatomically an ear, though it must have been almost useless in our dense air.
Guys, the celebrated Marseilles litterateur of the eighteenth century, was born with only one ear. Chantreuil mentions obliteration of the external auditory canal in the new-born. Bannofont reports a case of congenital imperforation of the left auditory canal existing near the tympanic membrane with total deafness in that ear.
Roosa of New York mentions the loss of hearing following a kiss on the ear. Dalby, in a paper citing many different causes of rupture of the tympanic membrane, mentions the following: A blow in sparring; violent sneezing; blowing the nose; forcible dilatation of the Eustachian canal; a thorn or twig of a tree accidentally thrust into the head; picking the ear with a toothpick.
The outlying remainder of the first gill-cleft is the rudiment of the external meatus. From its inner part we get the tympanic cavity, and, further inward still, the Eustachian tube. Connected with this is the development of the three bones of the mammal ear from the first two gill-arches; the hammer and anvil are formed from the first, the stirrup from the upper end of the second, gill-arch.
The plate of the stirrup is fixed by a membrane into the oval window of the inner wall of the tympanic chamber. These little bones are connected with each other and the tympanum by ligaments and moved by three tiny muscles. Two are attached to the hammer, and tighten and relax the drum; the other is attached to the stirrup, and prevents it from being pushed too deeply into the oval window.
This is formed into a part of the organ of hearing; from it are developed the external meatus, the tympanic cavity, and the Eustachian tube. We have already considered these remarkable structures, and need only point here to the interesting fact that our middle and external ear is a modified inheritance from the fishes.
Now the vibrations of the tympanic membrane are passed along the chain of bones attached to its inner surface and reach the stirrup bone. The stirrup now performs a to-and-fro movement at the oval window, passing the auditory impulse inwards to the internal ear. The membranous labyrinth occupies the central portion of the vestibule and the passages leading from it.
If it is destroyed, the fishes lose their balance and fall. The middle ear makes its first appearance in the amphibian class, where we find a tympanum, tympanic cavity, and Eustachian tube; these animals, and all terrestrial Vertebrates, certainly have the faculty of hearing.
The temperature sense is also a source of distraction in sleep, and it is a common experience to be awakened by extreme cold. The ears, too, may be the source of disturbance in sleep; for even though we are asleep, the tympanic membrane is always exposed to vibrations of air.