45 NORMAL HISTOLOGY AND ORGANOGRAPHY. 



of the scala media. The columnar cells just external 

 to this elevation are named the cells of Claudius. 



5. The lamina reticularis is a thin cuticular 

 structure which lies over Corti's organ and extends 

 from the outer rods as far as Hensen's cells. This 

 membrane has numerous small apertures into which 

 the outer hair cells project. 



6. The membrana lector ia is an elastic membrane 

 attached to the free margin of the lamina spiralis and 

 reaching outward as far as the outer row of hair cells. 

 This membrane has no nuclei and shows fine radial 

 striations. The membrane is supposed to act as a 

 damper to the hair cells. 



The Auditory Nerve. The auditory nerve divides 

 into two main parts, the ramus 'vestibularis and the 

 ramus cochlearis. The vestibularis divides into 

 three branches which are the macula acustica, utric- 

 uli, and the ampullae of the inferior and external 

 semicircular canals. The ramus cochlearis supplies 

 a branch to the macula acustica sacculi and one to 

 the ampulla of the posterior semicircular canal. The 

 remainder of the ramus cochlearis is distributed to 

 the hair cells of Corti's organ. Near the base of the 

 osseous spiral lamina there is situated, in a special 

 bony canal, a ganglion called the spiral ganglion of 

 the cochlea. The ganglion cells are bipolar, having 

 a dendrite that extends inward through the lamina 

 spiralis to the organ of Corti, and a neuraxis that 

 passes out the modiolus and thence to the medulla. 

 Some of the dendritic processes pass through the 

 tunnel of Corti, so called tunnel fibers, to reach the 

 outer hair cells. 



