140 THE AUDITORY NERVE AND COCHLEA, BY W. WALDEYER. 



We learn at once to distinguish the original soft parts of the 

 cochlea from their osseous capsule, formed by the petrous 

 bone ; and we learn to recognize the scalse as secondary struc- 

 tures formed around the principal canal of the cochlea, the 

 ductus cochlearis, the epithelial lining of which is destined 

 ultimately to constitute the very nucleus of the whole appa- 

 ratus. The arrangement, therefore, which commends itself as 

 being most appropriate for an histological description of these 

 parts is, in order : the osseous shell, with its periosteum ; 

 the structures termed the modiolus and the lamina spiralis ; the 

 scalse, with the parietal layer of the ductus cochlearis, composed 

 of connective tissue ; and lastly, the epithelial investment of 

 the latter. To this may be appended the consideration of the 

 terminal expansion of the nervus acusticus, in which also all 

 that is needful to be mentioned in respect to the histological 

 relations of the trunk of the auditory nerve will be given. 



CAPSULE OF THE COCHLEA AND MEMBRANA PROPRIA OF THE 

 DUCTUS COCHLEARIS. 



In regard to the osseous capsule of the cochlea, it may be 

 sufficient to call attention to the compact structure of its inner 

 layers, which are poor in bone cells, and form a kind of tabula 

 vitrea. On the contrary, the portions of the cochlea which 

 have ossified from mucous tissue, as the modiolus and lamina 

 spiralis, are of a more spongy nature, and contain numerous 

 medullary cavities, together with canals for bloodvessels and 

 bones. One of these canals, the canalis g un glionar is, /disco- 

 vered by Eosenthal (Claudius, Victor, 55), conceals the ganglion 

 spirale of the auditory nerve, and usually winds round the 

 modiolus at the base of the lamina spiralis (figs. 320 and 

 322). 



In Man this canal is traversed by many trabeculae of bone, so that 

 strictly speaking it forms a tubular system of cavernous spaces, the 

 cavities of which are occupied by the ganglion cells and nerve fibres. 



An account has already been given of the periosteum of the 

 cochlear wall, as far as regards its relations to the ductus 

 cochlearis, and I may refer to the preceding chapter for a 



