V 



THE SENSE OF HEARINC 



215 



Zona* pectinate, 

 tuitk fibres of 



..U'^'.'ij,.'// ll| I \ r 



Wn rviin mn-iih/S^Sir* 



: (J U|U U U V Ui^^.^s 



nil 



SflifocL 



Tootk-libe. 



projections 



oftimbus 



. 

 ' -of Umbfa 



rods of Corti ;ire attached, ;ind 

 the zona ])cctinata, extending 

 from the- lia.se of the outer rods 

 to the spiral ligament (Fig. 83). 

 The latter zone is somewhat 

 thicker and more iibrous. The 

 hasilar mombrune, as a whole, is 

 composed of a homogeneous sub- 

 stance, nucleated here and there, 

 with straight elastic fibres run- 

 ning from the spiral lamina to 

 the spiral ligament embedded in 

 it, so that from the surface it 

 a,] i] tears to be distinctly striated, 

 and in section the fibres are seen 

 as colourless dots in the homo- 



KM:. 84. Tanxrntial section ai-ross 

 pectiiiata ol' basilar mrinbraiif of 

 highly iiia.'-tiiti' 1 '!. 



tlif /"iia 



::. Uasilai inniiln an.- ami liiiilms vic\vi-cl 

 t'loin aluiM-. Mai, r iiilifi|. (G. H'-txiiis.) 



geneous ground-substance (Fig. 

 84). 



On the upper surface of the 

 basilar membrane is tlie com- 

 plicated epithelial formation 

 known as the organ of Corti, the 

 true peripheral apparatus which 

 transmits the auditory excitations 

 to the sensoriuui (Fig. 85). The 

 central part of this apparatus 

 consists of two sets of stiff rod - 

 like bodies standing some little 

 distance apart on the basilar 

 membrane, and inclined towards 

 each other so that they come 

 into contact above. These are 

 the rods of Oorti, each pair of 

 which forms an irregular pointed 

 arch, and the double row of in- 

 clined columns forms a tunnel 

 along the whole extent of the 

 cochlear canal. 



On the inner side of the inner 

 series of rods is a row of epi- 

 thelial cells surmounted by a 



