Animal life and intelligence . ratus. This consists of two small mem-branous sacs, with one of which three membranous loopedtubes, the semicircular canals, are connected; with theother is connected a spiral tube, the cochlear canal. Thesemembranous sacs and canals are filled with fluid, and aresurrounded by the fluid which fills the bony cavity inwhich they lie. This bony cavity has two little windows,one oval and the other round, across each of which amembrane is stretched. The oval membrane is in con-nection with the chain of auditory bones; and when thisis made to vibrate in and out, the me
Animal life and intelligence . ratus. This consists of two small mem-branous sacs, with one of which three membranous loopedtubes, the semicircular canals, are connected; with theother is connected a spiral tube, the cochlear canal. Thesemembranous sacs and canals are filled with fluid, and aresurrounded by the fluid which fills the bony cavity inwhich they lie. This bony cavity has two little windows,one oval and the other round, across each of which amembrane is stretched. The oval membrane is in con-nection with the chain of auditory bones; and when thisis made to vibrate in and out, the membrane of the roundwindow vibrates out and in. Thus the fluid around andwithin the membranous sacs and canals is set in vibration. The Senses of Animals. 263 And the parts are so arranged that the vibrations, inpassing from the oval to the round membrane, must runup one side and down the other side of the cochlear they run down they set in vibration a delicate mem-brane which is supported on beautiful arched rods (the. Fig. 27.—Diagram of ear. , tympanic membrane, to which is attached a chain of small bones stretching acrossthe cavity of the drum, the innermost of which, St., fits into the oval window. The vibra-tions are transmitted up one side and down the other side of the cochlear canal, , and thusreach the round window, ; is one of the semicircular canals, the other two areomitted; is the Eustachian tube connecting the cavity of the drum with the mouth-cavity. organs of Corti). And this membrane contains a numberof special hair-cells, so called because they bear minutehair-like structures. These are the special end-organs ofhearing. It has been suggested that the fibres of themembrane on the arched rods, which are of differentlengths and may be stretched with differing degrees oftension, respond to vibrations of different pitch. Thus thehair-cells on that particular part of the membrane wouldbe stimulated, and the note might be appreciated i
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