. A text-book of comparative physiology [microform] : for students and practitioners of comparative (veterinary) medicine. Physiology, Comparative; Veterinary physiology; Physiologie comparée; Physiologie vétérinaire. Mccnle at alligator, mw« ', «ber cell*; «, nerve-llber olniniiar auditory ceiii; A, brita. ._ auditory nerve In memora- HEARING. 56S or to occlusion of the Eustachian tube from excess of secretion, cicatrices, etc., in consequence of which the relations of atmos- pheric pressure become altered, the membrana tympani being indrawn, and the whole series of conditions on which
. A text-book of comparative physiology [microform] : for students and practitioners of comparative (veterinary) medicine. Physiology, Comparative; Veterinary physiology; Physiologie comparée; Physiologie vétérinaire. Mccnle at alligator, mw« ', «ber cell*; «, nerve-llber olniniiar auditory ceiii; A, brita. ._ auditory nerve In memora- HEARING. 56S or to occlusion of the Eustachian tube from excess of secretion, cicatrices, etc., in consequence of which the relations of atmos- pheric pressure become altered, the membrana tympani being indrawn, and the whole series of conditions on which the nor- mal transmission of vibrations depends disturbed, with the natural result, partial deafness. The hardness of hearing ex- perienced during a severe cold in the hettd (catarrh, etc.) is owing in great part to the ooolusion of the Eustachian tube, which may be either partial or complete. By filling one or both of the ears external to the mem- brana tympani with cotton-wool, one may satisfy himself how essential for hearing is the vibratory mechanism, which is, of course, under such circumstances inactive or nearly so; hence the deafness. When the middle ear is not functionally active, it is still possible, so long as the auditory nerve is normal, to hear vibra- tions of a body (as a tuning-fork) held against the head; though, as would be expected, discrimination as to pitch is very imperfect. Auditory impulaea originate within the inner ear—that is to say, in the vestibule and possibly the semicircular canals, but especially in the cochletu It is to be remembered that the. Fis. 411.—Diagram intended to illuitrate relative position of variona parts of ear (after Huxley). E, M, external auditory meatus; 3\, M, tympanic membrane; TV. tym- panum; Mall, malleus; Ine, incus; Stp, stapes: , fenestra avails; , fenes- tra rotunda; Eu, Eustachian tube; Jr. Z, membranous labyrinth, only one of the semicircular canals and Its ampulla being represented; Sea. V, Sea. T
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Keywords: ., bookauthormillswes, bookcentury1800, bookdecade1890, bookyear1890
