THE ORGAN OP HEARING. 447 



cochlear duct by a single layer of flat epithelial 

 cells. 



The outer wall of the scala media is the periosteal 

 lining of the bony cochlea which is thickened and 

 modified to form what is termed the ligamentum 

 spirale cochlea. The ligament has a projection, the 

 crista basilaris, to which the outer edge of the mem- 

 brana basilaris is attached. The inner surface of 



\ >= 



i 



m n n o p 



Fig. 308. Organ of Corti: At * the tectorial membrane is raised; c 

 outer sustentacular cells; d, outer auditory cells; /, outer pillar cells; g, 

 tectorial membrane; h, inner sustentacular cells; i,p, epithelium of'the 

 sulcus spiralis internus; k, labium vestibulare; e, tympanic investing 

 layer; m, outer auditory cells; n, w, nerve fibers which extend through 

 the tunnel of Corti; o, inner pillar cell; q, nerve fibers; b, b, basilar mem- 

 brane; a, epithelium of the sulcus spiralis externus; r, cells of Hensen; 

 s, inner auditory cell; /, ligamentum spirale (after Retzius). 



this wall is clothed with simple epithelium of the 

 columnar type, which in places appears to be strat- 

 ified and to possess darkly granulated cells. 



On the floor of the scala media and resting on the 

 basilar membrane is the complicated structure 

 termed the organ of Corti. This consists of the fol- 

 lowing structures: (i) Corti 's rods or pillars; (2) 



