462 



Dynamic Theory. 



FIG. 201. Transverse Section of a turn of the Cochlea. 

 1. Passage of the Scala Media. 5. Reissners membrane. 



2. Vestibuli. 6. Bone of the Modiolus. 



3. ' Tympam.* 7. Fibres of the Cochlear nerve to supply 



4. Basilar Membrane supporting Organs the Organs of Corti. 



of Corti. 

 Figures on the right Calcareous Otolith Crystals. 



FIG. 202. Scheme of the Scala Media and Organs of Corti. ( Landois & Stirling.) 

 1. Membrane separating the Scala Media 8. Outer rod of Corti. 

 from the Scala Vestibuli (Membrane of 

 Reissner). 



2. Cavity of Scala Media. 

 3. Outer wall of the Cochlea. 



4. Membrane of Corti covering the rods 

 and hairs. 



9. Basilar membrane. 

 10. Bony Center of Cochlea or Modiolus. 

 11. Cells in the sulcus or groove of Modio- 

 lus. 

 12. Nerve fibres passing to the hair cells. 



and hairs. 13. supporting cells. 



5. Outer hair cells, in 3 or 4 rows number- 14. Cells filling space near outer wall. 



ing 12,000 in all. 15, Reticular membrane. 



6. Inner hair-cells, one row about 4,000. 16. Cochlear Nerve. 

 7. Inner rod of Corti. 



reach the brain the compound effect is reproduced there. As there are 

 about 4,000 of these arches, and seven octaves include about all the 

 sounds we can distinguish, it follows that we ought to be able to culti- 

 vate a perception of about 570 intervals in each octave, or over 47 for 



