348 Dr. U. Pritchard on the [Mar. 2, 



they consist of several oval or columnar cells, which gradually merge into 

 the epithelial cells ; they form, in fact, the link between the hair-cells and 

 the epithelium. 



One or two similar cells, but with ill-defined outlines, are found forming 

 the inner boundary of the organ ; these I would term the inner support- 

 ing cells. 



(5) The Membrana Reticularis is one of the most peculiar structures in 

 the cochlea, and has never been satisfactorily described. It consists of a 

 fibrous network which covers the hair-cells and rods, and is firmly attached 

 to them. On either side it grows finer and finer, until lost among the 

 epithelial cells. The reticulate form of this membrane is only seen when 

 viewed from above ; to the inner side of the rods there is only one row 

 of regular circular meshes, through which the bristles of the inner hair- 

 cells project. Over the rods and their processes the membrane passes in 

 the form of long meshes, and in the region of the outer hair-cells it pre- 

 sents a very peculiar aspect. Here there are two forms of meshes — the 

 one elongated, called a phalanx, the other circular, called an annulus, so 

 arranged that each phalanx is surrounded by four annuli. Through the 

 annuli project the bristles of the outer hair-cells. 



Connected with this reticulate membrane, and, in my opinion, belonging 

 to it, are found three rows of fibrous cords, situated on the outer side of 

 each row of outer hair-cells. These cords, or trabecule, pass downwards 

 to the membrana basilaris, to which they are loosely attached by an en- 

 larged extremity. The trabecule have been described by other authors as 

 belonging to the hair-cells ; and Waldeyer figures them, together with the 

 hair-cells and cells of Deiters, as forming so many twin cells. My obser- 

 vations totally discountenance these views, as in the upper part of the 

 cochlea these three structures are seen to be quite separate, and again in 

 the human foetus the two cells are very far apart. 



(6) The Membrana Tectoria or Membrane of Corti. — Great miscon- 

 ception existed even down to the last few years as to the form and struc- 

 ture of this membrane. It was regarded as an elastic membrane of equal 

 thickness stretched straight across from the upper lip of the sulcus 

 internus to the corresponding projection of the ligamentum spirale ; nor 

 has it yet been properly described. I quite agree with later writers in 

 regarding it as a mucous mass secreted from the epithelial cells, and 

 therefore soft in the fresh state ; but I further regard it as only a thickened 

 portion of a layer which lines the whole ductus cochlea?, and which I 

 have traced right round. 



The thickened portion forming the membrana tectoria commences at 

 the attachment of the membrane of Eeissner to the limbus, and passes 

 over the teeth of the limbus as a layer of equal thickness ; then passing 

 outwards rapidly increases in thickness as it covers the organ, and gra- 

 dually tapers off to the thin general layer, which, as already stated, lines 

 the rest of the ductus cochleae. 



