LAMINA SPIRALIS OF THE COCHLEA. 283 



the extremities of the cochlear nerve-filaments pass to the 

 vestibular surface of the membrane. The cochlear nerves, 

 therefore, instead of being distributed, as has hitherto been 

 supposed, on the tympanic aspect of the lamina spiralis, pass 

 through it to its vestibular aspect ; its entire tympanic sur- 

 face, and the nerves in their transit across that surface, from 

 the fissure in the osseous to the orifices in the membranous 

 portion, being covered by the fibro-serous lining membrane of 

 the osseous labyrinth. It thus appears that all the complex 

 structures in connection with the lamina spiralis, usually so 

 called, of the cochlea, are situated on its vestibular aspect. 



These structures are 1. The habenula sulcata, situated 

 chiefly on the osseous lamina, and discovered by Todd and 

 Bowman ; 2. The habenula denticulata, situated on the mem- 

 branous lamina, discovered by Corti, and latterly ascertained 

 by Kolliker to be connected with the cochlear nerves ; 3. 

 The membrane of Corti, covered on its vestibular surface by 

 the serous lining membrane of the osseous labyrinth, first 

 partially recognised by Corti, but latterly more fully described 

 by Claudius ; 4. Large vesicular cells which occupy the 

 space between the membrane of Corti and the lamina spiralis, 

 usually so called, first recognised by Corti, but more precisely 

 determined by Claudius. 



The habenula sulcata is a structure of cartilaginous aspect, 

 which, rapidly increasing in thickness as it advances to the 

 outer margin of the osseous lamina, inclines over and beyond 

 that margin so as to form the sulcus spiralis of Huschke. It 

 consists of columns, which at its thin inner edge are set per- 

 pendicular to the surface of the subjacent bones, and therefore 

 expose their free extremities on its vestibular aspect. To- 

 wards its thick or outer edge the columns become more and 

 more inclined, so as to expose more and more of their sides, 

 and at the edge itself they form a series of elongated, slightly 

 clavate and flattened, clear glistening teeth, which project 



