36 THE EXTERNAL AND MIDDLE EAR, BY J. KESSEL. 



fusiform nucleated elements, and not unfrequently small carti- 

 lage cells, either scattered or arranged in rows. 



From the above description it appears that all the layers 

 of the mem'brana propria are intimately connected with the 

 tendinous ring. I must therefore corroborate Gruber (8) in 

 his recently made statement, that the circular fibres can be 

 distinctly followed into the tendinous ring; but may add, that 

 they run at some distance from each other, and are severally 

 given off at very acute angles from the latter. The fibres, as 

 they are given off collectively in the vicinity of the ring, 

 form groups, the thickness of which is equal to that of the 

 epidermis, cutis, and mucous membrane collectively ; by the 

 tension of these fibres the radii of the surface of the tympanic 

 membrane are rendered convex towards the auditory meatus. 

 Towards the centre of the tympanic membrane the circular 

 fibres diminish again in thickness, and are altogether absent at 

 the lower third of the handle of the malleus and the adjoining 

 parts. The circular fibrous layer is particularly well marked 

 at the periphery of the anterior and superior segment, because 

 the fibres here present, which proceed from the tendinous ring, 

 become associated with those which come in an oblique direc- 

 tion from the posterior and superior wall of the auditory 

 meatus, and extend across the already described triangular 

 space below the Bivinian fissure. 



Thus, with the exception of the above-mentioned neutral 

 portion, the circular layer is everywhere present. The varying 

 diameter of the circular layer, like the varying thickness of 

 the cutis, which, as above stated, is most strongly expressed at 

 the periphery and along the handle of the malleus, renders it 

 impossible to give an average thickness to the membrana 

 tyrnpani. It amounts, in the two last-named spots, to about 

 01 of a millimeter ; whilst in the intervening parts, where the 

 cutis diminishes in thickness, and the circular fibres become 

 thinner or are altogether absent, it is only half as much as 

 this, or still less. Moreover, the membrana propria is attached 

 to the handle of the malleus, but the views that are held upon 

 the mode and nature of this attachment are widely divergent. 

 According to v. Troeltsch (45), the handle of the malleus is 

 introduced between the two fibrous layers (radial and circular 



