A text-book of the diseases of the ear and adjacent organs . 12 SIZE AND DIRECTION OF THE EXTERNAL MEATUS. on a section through the outer pole of the membrana tympani these diametersare 8*1 and 46 mm. respectively. The lengths of the different walls from the external orifice of the ear to theinsertion of the membrana tympani are unequal. V. Troltsch in his measure-ments assumes as the exterior boundary of the meatus a sagittal plane, passingthrough the posterior margin of the orifice, and according to him the lengthof the superior wall amounts mm., that of the inferior to 26 mm., thatof
A text-book of the diseases of the ear and adjacent organs . 12 SIZE AND DIRECTION OF THE EXTERNAL MEATUS. on a section through the outer pole of the membrana tympani these diametersare 8*1 and 46 mm. respectively. The lengths of the different walls from the external orifice of the ear to theinsertion of the membrana tympani are unequal. V. Troltsch in his measure-ments assumes as the exterior boundary of the meatus a sagittal plane, passingthrough the posterior margin of the orifice, and according to him the lengthof the superior wall amounts mm., that of the inferior to 26 mm., thatof the anterior to 27 mm., and that of the posterior wall to 22 mm. On anaverage the length of the whole meatus is 24 mm., of which more than one-third is taken up by the cartilaginous portion. The meatus in its course from the external orifice to the mem-. Fig. 13.—Horizontal Section of the External Meatus. «, Concha ; b, Tragus ; c, Place of attachment of the cartilaginous portion ; d, Mas-toid process ; e, Anterior wall of the meatus ; /, Sin. meat, audit, extern. ; ;/,Membrana tympani; h, Tympanic cavity (left ear). brana tympani displays several curves, which deserve full considera-tion in regard to examinations of the membrana tympani, as well asin respect to operations in the meatus. Although the whole meatusappears spirally twisted about its axis (Fig. 14) it may on the wholebe assumed that the cartilaginous portion in passing inwards turnsbackwards and upwards, the osseous portion forwards and down-wards. The longitudinal axes of the two portions of the meatus thereforeform an open angle forwards and downwards, and as the meatusfrom the place of union of the two portions slopes both outwardsand inwards, the inferior part of the external orifice and of themembrana tympani must lie lower than the other parts of themeatus. Accor
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Keywords: ., bookcentury1800, bookdecade1890, booksubjecteardiseases, bookyear
