File:A text-book of physiology for medical students and physicians (1911) (14798791673).jpg

Identifier: textbookofphysio1911howe (find matches)
Title: A text-book of physiology for medical students and physicians
Year: 1911 (1910s)
Authors: Howell, William H. (William Henry), 1860-1945
Subjects: Physiology
Publisher: Philadelphia, London, W.B. Saunders company
Contributing Library: Columbia University Libraries
Digitizing Sponsor: Open Knowledge Commons

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cube with black top resting on two others with blacktops, to one of two cubes with black bottoms resting upon a single cube with blackbottom. Still other figures may appear from time to time. focuses for the point a, this point may be held in the foregroundand the second of the above appearances be seen. While if theeyes are accommodated strongly for point b, it will be broughtforward and the first of the two appearances described is broughtinto view. PHYSIOLOGY OF THE EAR. CHAPTER XX. THE EAR AS AN ORGAN FOR SOUND SENSATIONS. In discussing the physiology of the ear it is necessary to considerthe functional importance of its various parts, the external earconsisting of the lobe or pinna, the external auditory meatus, andthe tympanic membrane; the middle ear, with its chain of ossicles,its muscles and ligaments, and the Eustachian tube; and the internalear, with its cochlea, vestibule (utriculus and sacculus), and semi-circular canals. The eighth cranial or so-called auditory nerve is
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Fig. 167.—Semidiagrammatic section through the right ear (Czermak): G, Externalauditory meatus; T, membrana tympani; P, tympanic cavity; o, fenestra ovahs; r, fen-estra rotunda; B, semicircular canal; <S, cochlea; Vt, scala vestibuli; Pt, scala tympani;E, Eustachian tube. distributed entirely within the internal ear; the fibers of the coch-lear branch, which alone perhaps are concerned with hearing, endamong the sensory nerve cells of the cochlea, while the vestibularbranch supplies similar sense cells situated in the utriculus, sacculus,and the ampullae of the semicircular canals. We may considerfirst the functions of the ear in respect to the sensations of sound.The somewhat complicated anatomy of the parts concerned should 378 EAR AS AN ORGAN FOR SOUND SENSATIONS. 379 be obtained from the special works on anatomy or histology. Forthe purposes of a physiological presentation the schematic figureemployed by Czermak and reproduced in Fig. 167 will suffice toexhibit the general an

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