A text-book of the diseases of the ear for students and practitioners . ernal wall of thetympanic cavity extend-ing into the Eustachiantube. (Right ear.) 14 DISEASES OF THE EAR anterior and inferior walls of the meatus reach internally beyondthe posterior and superior walls (Figs. 9 and 10). One differ-entiates, therefore, a vertical and a horizontal inclination. Theformer, according to Schwalbe, is designated inclination, thelatter declination. Bezolds measurements on corrosion prepara-tions gave the average angle as 27°-35°. V. Troltsch estimatedthe angle which the plane of the membrane form
A text-book of the diseases of the ear for students and practitioners . ernal wall of thetympanic cavity extend-ing into the Eustachiantube. (Right ear.) 14 DISEASES OF THE EAR anterior and inferior walls of the meatus reach internally beyondthe posterior and superior walls (Figs. 9 and 10). One differ-entiates, therefore, a vertical and a horizontal inclination. Theformer, according to Schwalbe, is designated inclination, thelatter declination. Bezolds measurements on corrosion prepara-tions gave the average angle as 27°-35°. V. Troltsch estimatedthe angle which the plane of the membrane forms with thesuperior wall at an average of 140°. According to J. Pollak,there is no perceptible difference in the inclination of themembrane in the new-born and in the adult. It is, however, tobe noted that the separate portions of the membrane exhibit adifferent inclination to the horizontal. The anterior inferiorquadrant formsan angle of 75°-85° with the axis of the meatuswhen the head is in a vertical position; the posterior superiorquadrant, an angle of 150°.. Fig. 15.—External Surface of the Membrana Tympani (Natural Size). a, Short process of the malleus ; b, Inferior extremity of the handle of the malleus(umbo) ; c, Membrana flaccida Shrapnelli ; d, Fossa mandibulars ; c, Mastoidprocess ; /, Section of the zygomatic process. (Right ear.) Curvature.—The obliquely-placed membrane is curved in sucha manner that its concavity is directed outwards, its convexityinwards (Fig. 9, c). The greatest point of curvature, the umbo,corresponds to the inferior extremity of the manubrium whichis enclosed in the layers of the membrane. Through the inwardtraction of the handle, the membrane appears membrane appears, as a whole, concave externally ; still,there is a deviation from this regular curvature, in so far as theanterior and inferior portions between the umbo and the peripheryare decidedly convex externally (Fig. 9). This is brought aboutpartly by the inwa
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectear, booksubjecteardi
