A text-book of the diseases of the ear and adjacent organs . ana tym-pani : d. Exterior wall ofthe cavity extending intothe Eustachian tube. (Rightear.) ( URVATUKE OF THE MEMBKANA TYMPANI. 15 and 10), Be/olds measurement on corrosion preparations gives the averageangle as 27-35°. Y. Troltsch places the angle which the plane of the nieni-brane forms with the superior wall of the meatus at an average of 140°. Dr. J. Pollak maintains that there is no perceptible difference between theinclination of the membrane in the new-born infant and in the adult. Curvature of the Membrana Tympani.—In the abo
A text-book of the diseases of the ear and adjacent organs . ana tym-pani : d. Exterior wall ofthe cavity extending intothe Eustachian tube. (Rightear.) ( URVATUKE OF THE MEMBKANA TYMPANI. 15 and 10), Be/olds measurement on corrosion preparations gives the averageangle as 27-35°. Y. Troltsch places the angle which the plane of the nieni-brane forms with the superior wall of the meatus at an average of 140°. Dr. J. Pollak maintains that there is no perceptible difference between theinclination of the membrane in the new-born infant and in the adult. Curvature of the Membrana Tympani.—In the above-described obliqueposition the membrana tympani is not stretched out as a plane surface, but iscurved in such a manner that it turns its concavity outwards, and its con-vexity towards the interior of the tympanic cavity (Fig. 9, e). The deepestpart of the curvature, the so-called umbo, corresponds with the inferiorextremity of the handle of the malleus, which is enclosed in the layersof the membrana tympani. By the traction of this handle inwards the. h a c d Fig. 16.—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, Cavitas glenoidalis ; e, Mastoid pro-cess ; J\ Section of the zygomatic process. (Right ear.) membrane appears hollowed out in a funnel-shaped manner. The interiorconvexity is common to the membrana tympani as a whole, but on closerobservation it is seen that the anterior and inferior portions of the from the umbo towards the periphery, show a slight curvature witliexterna] convexity (Fig. 9). This partial bulging out, as opposed to thecurvature of the membrane, is due partly to the drawing inwards of themembrane by the traction of the handle of the malleus, partly to the actionof the circular fibres upon the radiating fibrous layers (Helmholtz). Thatportion of the membrane which is situated behind the han
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Keywords: ., bookcentury1800, bookdecade1890, booksubjecteardiseases, bookyear
