Politzer's text-book of the diseases of the ear and adjacent organs : for students and practitioners / translated at the request of Professor Politzer and edited by James Patterson Cassells.

  • Politzer, Adam, 1835-1920.
Date:
1883
Catalogue details

Licence: Public Domain Mark

Credit: Politzer's text-book of the diseases of the ear and adjacent organs : for students and practitioners / translated at the request of Professor Politzer and edited by James Patterson Cassells. Source: Wellcome Collection.

Provider: This material has been provided by University of Bristol Library. The original may be consulted at University of Bristol Library.

    21/858 (page 1)
    ANATOMICAL DIVISION OF THE EAR. The sensations whicli we call perceptions of soimd, reach our consciousness by the specific excitation of the nerve of hearing. This excitation always results, when the medium which sur- rounds us is caused to vibrate by the oscillations of elastic bodies, the vibrations being transmitted to the nerve of hearing. This perception of sound is principally brought about by the excitation of the peripheral expansion of the auditory nerve. The dehcate terminations of this nerve lie upon membranous supports, which are siurrounded by an aqueous fluid in a cavity partly formed by rigid walls. These membranous supports serve as a medium for the transfer of the waves of sound, which reach the auditory fluid from the outer world, to the extremities of the auditory nerve. The most primitive form of auditory apparatus among the lower classes of animals consists of an expansion of the auditory nerve upon a small membranous vesicle, the auditory vesicle (or vestibular saccule). This simple hearmg apparatus assumes in the higher animals a more comphcated form, there being added to the vestibular saccule several membranous tubes (semichcular canals), generally three in number. In the most highly deve- loped vertebrata, to these two parts of the labyrinth, the vesti- bular saccule and the semicircular canals, there is added a third, the cochlea, in which a portion of the auditory nerve is spread ■out upon a membranous lamella. The vibrations of elastic bodies, however, do not reach the -auditory nerve immediately, but are conveyed to it through a more or less comphcated conducting apparatus. In aquatic animals the waves of sound, proceeding through the water, are communicated to the hard parts of the head, and through those to the auditory fluid and the auditory nerve.' Animals living in the air possess a sound-conductmg apparatus, adapted for the reception of atmospheric vibrations. The con- struction of this apparatus is the same in principle in all the separate classes of animals, but its form shows ' considerable variety.