SECT. 234.] ZONA DENTICULATA. 593 



it, presents the following arrangement : In the neighbourhood of 

 the foramina of the habcimla perforata (mihi) peculiar rod-like 

 structures take their origin ; these are the Cortian fibres, which 

 taken together form a sort of membrane in the whole length of 

 the lamina basilaris, lying near that lamina, and being fastened 

 to it at its outer end. The membrane formed by the Cortian 

 fibres is convex in the middle (rising up towards the membrana 

 Cortii), and may best be compared to a broad but short bridge. 

 More narrowly investigated, this peculiar apparatus is found to 

 consist of two sorts of pieces, the inner and outer Cortian fibres, 

 which although agreeing with each other in many particulars, yet 

 differ in many respects, especially in their numbers ; for the inner 

 fibres are more numerous than the outer (as Claudius first pointed 

 out), so that three of the inner fibres correspond to two of the 

 outer (fig. 244, a, b). The inner fibres commence in a very regular 

 series near the foramina of the habenula perforata, where they are 

 about croo 1 5"' to 0-002'" in breadth, and soon present on the side 

 turned towards the basilar membrane a nucleated swelling, which 

 is produced, according to Schultze, only by a cell lying on them : 

 they then run outwardly, with a gentle slope upwards, parallel to 

 each other, but separated by fissure-shaped interspaces, and end 

 by broadened (o'oo24'") extremities which lie close together and 

 are more raised than the other parts of the fibre ; these were 

 erroneously regarded by Corti as being separate pieces, and were 

 named by him, Coins articulaires internes. Upon these follow the 

 outer Cortian fibres, beginning by a slight annular constriction, 

 and another similar enlargement of the fibre up to 0-0035'" {Coins 

 articulaires externes, Corti); these fibres are fewer in number and 

 broader than the inner series (fig. 244, b). The outer Cortian 

 fibres bend downwards back again towards the basilar membrane, 

 become narrowed in the middle, and expanded at their further 

 extremities into a triangular end, on the under side of which also, 

 I have often found a nucleated swelling; by these ends the fibres 

 come into contact with the basilar membrane, but are always 

 easily separable from it, and have no intimate connexion whatever 

 with it. The entire length of a Cortian fibre, including the outer 

 and inner portions (the former of which is usually somewhat the 

 longer), amounts to 0-037'" to °'°5o"'; and as far their other 

 properties, they have not the smallest resemblance chemically to 

 the lamina spiralis membranacea, with which they have been classed 

 by Corti and some other recent writers; for, on the very contrary, 

 they are tender and easily destroyed fabrics, dissolving instantly 



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