ORGAN OF CORTL 



541 



tain solid structures seated on the basilar membrane and 

 forming the organ of Corti; the rest of its cavity is filled 

 with endolymph, which communicates with that in the 

 sacculus. 



The Organ of Corti. This contains the^nd organs of 

 _the cochlear nerves. Lining the sulcus spiralis are cuboi- 

 ~dal cells; on tne inner margin of the basilar membrane they 

 become columnar, and then are succeeded by a row which 

 bear on their upper ends a set of short stiff hairs, and con- 

 stitute the inner hair-cells, which are fixed below by a 

 narrow apex to the basilar membrane; nerve-fibres enter 

 them. To the inner hair-cells succeed the rods of Corti 



B 



FIG. 148. The rods of Corti. A, a pair of rods separated from the rest; B, a 

 bit of the basilar membrane with several rods on it, showing how they cover in 

 the tunnel of Corti; i, inner, and e, outer rods; 6, basilar membrane; r, reti- 

 cular membrane. 



(Co, Fig. 147), which are represented highly magnified in 

 Fig. 148. These rods are stiff and arranged side by side in 

 two rows, leaned against one another by their upper ends 

 so as to cover in a tunnel; they are known respectively as 

 the inner and outer rods, the former being nearer the 

 lamina spiralis. Each rod has a somewhat dilated base, 

 firmly fixed to the basilar membrane; an expanded head 

 where it meets its fellow (the inner rod presenting there a 

 concavity into which the rounded head of the outer fits) ; 

 and a slender shaft uniting the two, slightly curved like an 

 italic /. .The inner rods are more slender and more 

 numerous than the outer, the numbers being about 6000 

 .and 4500 respectively. Attached to the external sides of 

 the heads of the outer rods is the reticular membrane (r. 



