282 LAMINA SPIRALIS OF THE COCHLEA. 



XIV. — ON THE LAMINA SPIEALIS OF THE 



COCHLEA. 



The lamina spiralis of the cochlea, instead of being, as hitherto 

 supposed, a single layer, osseous in the inner, and membran- 

 ous in the outer portion of its extent, is a double structure, 

 with numerous complex arrangements in its interior. 



The osseous and membranous portions of the lamina 

 spiralis, as liitherto understood, may be considered as the 

 basis of the entire complex structure as it is now ascertained. 



The osseous portion of the lamina contains the cochlear 

 nerves in closely-arranged canals, which, at its outer margin, 

 coalesce in a chink or fissure, which contains the ganglion 

 recently discovered by Corti, and affords exit to the nervous 

 filaments. 



The membranous portion of the lamina consists, as 

 discovered by Todd and Bowman, of a membrane which, 

 except at its outer and inner margins, is closely streaked in 

 the direction of the radius of the cochlea, and hence denomi- 

 nated zona pectinata. The outer margin of the membrane is 

 attached by means of a fibro-nucleated texture to the accessory 

 spiral lamina of Huschke, and to the neighbouring groove. 

 This fibro-nucleated structure is the cochlear muscle of Todd 

 and Bowman — the spiral cochlear ligament of Kolliker. The 

 inner margin of the membrane is attached to that lip of the 

 fissure of the osseous lamina which is next the apex of the 

 cochlea, but so as to leave numerous orifices or more or less 

 oblique canals, through which, as Kolliker has ascertained. 



