. Human physiology : designed for colleges and the higher classes in schools, and for general reading. is fact that hasgiven the name of labyrinth to the whole of the internal vestibule opens into the cochlea at its base. Now, thecochlea is so divided, that the passage into which the vestibuleopens, runs around the pillar in the middle of it to its top,making just two turns and a half. It there opens into anotherpassage, which makes two turns and a half back to the base ofthe cochlea. This passage does not end in the vestibule wherethe other began, but it ends in the round hole r, whic
. Human physiology : designed for colleges and the higher classes in schools, and for general reading. is fact that hasgiven the name of labyrinth to the whole of the internal vestibule opens into the cochlea at its base. Now, thecochlea is so divided, that the passage into which the vestibuleopens, runs around the pillar in the middle of it to its top,making just two turns and a half. It there opens into anotherpassage, which makes two turns and a half back to the base ofthe cochlea. This passage does not end in the vestibule wherethe other began, but it ends in the round hole r, which opensinto the cavity of the tympanum. This disposition of theparts of the cochlea may be seen in Fig. 152, which representsit as opened to show the arrangement of the walls of the twowinding galleries. The pillar in the middle, around whichthese dividing walls are fastened, expands in the top into whatis called a cupola, where the two spiral galleries communicatetogether. With this description, you can understand in what THE EAR. 281 Distribution of the nerve of hearing in the cochlea. FIG. THE COCHLEA OPENED. directioos the vibration is transmitted, when it is received fromthe stirrup-bone, at the door of the labyrinth, by the membranewhich covers it. It travels one way up the fluid in the threesemi-circular canals. It travels another way through one spiralgallery in the cochlea to the cupola, and then down the otherspiral gallery, reaching at length the membrane of the fenestrarotunda, or round window. 423. I will now describe to you the arrangement of thebranches of the nerve of hearing in these passages. The ar-rangement is different in the vestibule and the semi-circularcanals from what it is in the cochlea. In all the cavities of thelabyrinth, there is a thin, delicate lining of membrane, whichsecretes a watery fluid. In the vestibule and semi-circularcanals, there is a second membrane. This is separate from thefirst membrane, and lies loose in the cavities. It ma
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