An academic physiology and hygiene .. . ransmit them, by meansof the auditory nerve, to the brain. While the middle earis an air-chamber, the internal ear is a water divisions are a central chamber, or vestibule ; the spi-ral tubes, or cochlea; and the semi-circular canals—allforming a continuous cavity. 2. The Vestibule. — This is the central, egg-shaped por-tion of the labyrinth between the semi-circular canalsand the cochlea. It communicates with the drum-cavityby means of two small openings, which, from their shapes,are called the oval window and the round window. In thelivin
An academic physiology and hygiene .. . ransmit them, by meansof the auditory nerve, to the brain. While the middle earis an air-chamber, the internal ear is a water divisions are a central chamber, or vestibule ; the spi-ral tubes, or cochlea; and the semi-circular canals—allforming a continuous cavity. 2. The Vestibule. — This is the central, egg-shaped por-tion of the labyrinth between the semi-circular canalsand the cochlea. It communicates with the drum-cavityby means of two small openings, which, from their shapes,are called the oval window and the round window. In theliving body these windows are closed by firm mem- 1 LAB-Y-RINTH (Or. lahitrin1Hhos). A maze; a building with many winding 2 Fil-a-ments, tiny, thread-like ei 344 ACADEMIC PHYSIOLOGY. branes, similar to that of the drum-head. The foot-plateof the stirrup-bone is joined firmly to the membrane ofthe oval window, and thus the connection between thedrum-head and the labyrinth and nerve of hearing is madecomplete by the chain of little Fig. 58. —Interior of the Left Labyrinth, highly magnified. to a, the cochlea ; k, the hollow axis about which the two canals wind two and a halfturns; i to 4, the semi-circular canals; m, the vestibule, in which are ?/, the fenestra ro-tunda (round window), and o, the fenestra ovalis (oval window). 3. The Cochlea, or Snail-shell. — This portion of the inter-nal ear is a bony tube twisted two and a half times abouta bony pillar, being similar to a snail-shell. It is divided,in part, into two spiral passages by a bony shelf. If aninsect could leave the vestibule opposite the oval window,it might pass into the upper of these spiral stairways,crawl to the summit, and descend by the lower stairway tothe round window HEARING. 545 4. The nerve of the cochlea, after passing into the bony pillar, divides into many tiny brandies of varying length whi< s sad out upon the bony shelf, like the strings of a harp or piano, and form the so
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