jo6 AYERS. [Vol. VI. 



freely projecting membrane, however, scarcely allows of cross- 

 section without dislocation, and the question is only to be 

 decided by cross-sections. A good embedding method will 

 probably answer it sometime. 



On the under surface of the membrane in the rabbit there 

 is no spiral ridge such as Hensen lately described. The mem- 

 brane grows thicker rapidly after leaving the hmbus, and the 

 upper surface is convex in a radial direction. 



In the middle spiral, the membrane is thickest at its outer 

 border, and the upper and lower surfaces are here bound to- 

 gether by a relatively broad, convex edge plate. On the upper 

 surface, somewhat within the edge, is a thick shining string 

 or cord, that appears somewhat circular in cross-section, runs 

 spirally, and is intimately bound to the surface. From it there 

 passes out over the membrane a net of fine fibres running diago- 

 nally inwards, or really, with reference to the cochlear apex, 

 from without and above downward and inward. The meshes of 

 this fibre net of Loewenberg are oval fissures in its substance. 

 In sections of the membrana tectoria this net appears as scat- 

 tered granules over the surface of the membrane. This net 

 does not extend further inward than to about the middle of the 

 free zone ; here the fibres become pointed and end themselves. 



Of what is this membrane composed } 



When one studies it fresh in aqueous humor, it is clear, 

 transparent, gelatinous, firmly soft, somewhat elastic, so that it 

 may be slightly stretched. When released, it contracts ; when 

 drawn too strongly, it splits diagonally and transversely, i.e. in 

 the direction of the fibres of which it is composed. It appears 

 while fresh to be striated diagonally from above and outward 

 toward its inner and lower border, and under higher power it 

 is seen to be made up of uncountable fibres which run in the 

 given direction. Stained with fuchsin, the fibres appear sharper, 

 rose-red, and they are separable by teasing. With gentle press- 

 ure the membrane is compressible, but returns to its normal 

 shape on removal of pressure. Chromic and osmic acids make 

 its substance firmer, but its composition out of fine fibres is 

 just as distinct. Although these fibres stick closely to each 

 other and are separable only with difficulty, one cannot distin- 

 guish a cement substance between them. But a minimum 

 amount of such a substance is to be predicated as present 



