THE OSSEOUS LABYRINTH. 



103 



ting the nerve-fibres of 1| turns of the cochlear tube, the former being continued 

 into the central canal of the modiolus and transmitting the nerve-fibres for the 

 uppermost turn. 



The osseous spiral lamina is a thin, flat plate, growing from the modiolus, and 



vcfitibidi helic'trcma 



lamina spiralis scala tympani 

 membranacca 



expansion of cochlear nerve 

 Fig. 113. DIAGRAMMATIC VIEW OF THE OSSEOUS COCHLEA LAID OPEN. (Arnold.) 



projecting into the spiral tube, so as to divide it partly into two. It does not reach 

 farther than about half-way towards the outer wall of the spiral tube. Close to the 



scala vcstibuli 



v. . ... 



scala tympani lamina spiralis ossea tncatus auditorius inttrnus (fovea cochlea?) 



Fig. 114. VIEW OF THE OSSEOUS COCHLEA DIVIDED THROUGH THE MIDDLE. (Arnold.) 



npex of the cochlea, it ends in a hooklike process (hamulus), which partly bounds 

 the helicotrema. Opposite the lamina spiralis at the commencement or base of the 

 cochlear tube is another bony lamina (secondary spiral lamina) which nearly meets 

 the spiral lamina, so that there is here only a narrow cleft between the two. 



The lamina is dense at its free edge ; but nearer the modiolus its internal 



