THE ORGAN OF CORTI. 



Fig. 522. 



765 



Fig. 522. DIAGRAMMATIC OUTLINE OP A RADIAL SECTION THROUGH THE LAMINA SPIRALIS 

 MEMBRANACEA, ORGAN OF CORTI, &c. (after Kolliker, Heule, and other*). --^ 



This figure may be regarded as a more enlarged and explanatory view of the part of 

 fig. 518 representing the organ of Corti : S V, part of the scala vestibuli ; C C, canalis 

 cochleae ; S T, scala tympani ; R, membrane of Reissner, forming the partition between 

 the scala vestibuli and the canalis cochleae ; I s o, a small part of the lamina spiralis ossea 

 cut in the direction of one of the canals transmitting the cochlear nerves, nc; p, perios- 

 teum lining the scala tympani ; Us, limbus laminae spiralis, presenting a great thickening 

 of the periosteum, in which over the extremity of the osseous spiral lamina is found the 

 sulcus spiralis s s, and upon the upper surface of which are the toothed projections ; I v, 

 labium vestibulare ; 1 1, labium tympanicum of the sulcus spiralis ; Ivtolsp, the lamina 

 spiralis meinbranacea with its contained parts ; mt, membrana tectoria passing from the 

 limbus laminae spiralis to the outer wall of the cochlear tube ; mb, membrana basilaris, 

 stretched from the labium tympanicum to the outer wall of the cochlear tube, where it 

 expands in the ligamentum spirale, I sp ; the part marked by the letters m b, between two 

 short dotted lines, forms the zona tecta or z. arcuata ; the part indicated by m b' and between 

 the adjacent dotted lines is the zona pectinata ; C, the organ of Corti ; i, the internal rods ; 

 e, the external rods ; these are set by their lower flattened ends on the basilar membrane, 

 and are articulated together at their upper parts, a, the inner overlapping the outer ; a 

 nucleus is seen close to the base of each of the rods close on the basilar membrane ; m r, 

 membrana reticularis, stretched to the outer wall of the cochlea, pc; below mr, the cells 

 of Corti lying obliquely on the outer rods, and between them the cells of Deiters, and 

 between these and the outer wall of the cochlea epithelial cells ; between a and mr, are 

 indicated the perforations through which the hair-like terminations of the cells of Corti 

 project : the sulcus spiralis is seen filled with cylindrical and other epithelium. 



sistency to cartilage. The inner rods are more closely set and more nume- 

 rous than the outer, and appear generally to be of a uniform breadth, 

 flattened, and with a nucleiform body placed subjacent to the lower 

 extremity. The outer rods are narrow and cylindrical in their shafts, and 

 expanded at the lower extremity, which has a nucleiform body subjacent to 

 it, as in the case of the inner rods. At their upper ends where they meet 

 together, both sets of rods are thickened, and the parts which are in con- 

 tact (coins articulaires externes et internes of Corti) have the appearance of 

 quadrilateral plates directed outwards so that those of tUe inner row lie 

 over those of the outer row, and those of the outer row are bent backwards 

 from the direction in which the rods to which they belong are placed. 

 From the junction line of the rods there extends outwards an extremely 

 delicate network, the lamina reticularis of Kolliker (i. velamentosa, Deiters), 

 which, it may be gathered from different accounts, is mainly constructed of 

 a layer of squamous cells so disposed as to leave at least three rows of 

 large perforations between them, and which are cemented together by a net- 

 work of intervening substance which is sometimes detected when the cells are 

 not. At its inner margin this lamina is united by flat plates to the inner 



