40 



THE EXTERNAL AND MIDDLE EAR, BY J. KESSEL. 



tral membranous expansion to the periphery, and streaming 

 out over the circular fibres like a fan interweave with one an- 

 other. Owing to the radiation of the adjoining trabeculse, the 

 margin of the middle membranous expansion forms a series ol 

 curves, the concavities of which are directed towards the peri- 

 phery. Owing to their peripheric attachment, these arches 

 leave hiatuses varying in their number, form, and position. 

 The central membranous expansion may also exhibit similar 

 gaps. The structure of the framework is further rendered 



Fig. 281. 



Fig. 281. Part of the posterior segment of the membrana tympani, 

 seen with a low power, a, The membrane itself lying beneath the 

 epithelium, with its processes stretching towards b, the tendinous ring ; 

 the dark plexus represents bloodvessels. From a specimen stained 

 with chloride of gold. 



complicated by the circumstance that the above-mentioned 

 radiating trabeculse do not all lie in the same plane ; some, in- 

 stead of going towards the tendinous ring, penetrate deeply 

 between the radial and circular fibres into the above-described 

 free spaces remaining between the circular fibres, and expanding 

 here form a trabecular tissue, so as to leave a number of spaces 



