NERVES OF COCHLEA. 



125 



contained in separate canals in the bony lamina, but afterwards spreading out 

 into a stratum of intermingling fibres, to be again gathered up, near the edge 



limbvs 



membrana tectoria 



outer hair- cells 

 I 



nerve fibres 



inner rod t'as basilar outer cells of Deiters 

 spirale membrane rod 



Fig. 145. SECTION THROUGH THE ORGAN OF CORTI OP THE MIDDLE TURN OP THE HUMAN COCHLEA. 



(GK Retzius.) Highly magnified. 



of the osseous lamina, into conical bundles which turn abruptly upwards, and 

 passing through the elongated apertures previously described (p. 112 and fig. 132, 



Fig. 146. ENDING OP NERVE-FIBRES IN THE 



COCHLEA, SHOWN BY Q-OLGl's METHOD. (Gr. 



Retzius. ) Much magnified. 



g, a cell of the spiral ganglion ; i. h., inner 

 hair-cells ; o.A., outer hair-cells, \vith the 

 nerve-fibres running spirally between the cells. 



lose their medullary sheath, and enter 

 the epithelium in the region of the 

 inner hair-cells (fig. 145). Some of 

 the nerve-fibres appear to end here by 

 ramifying with a spiral course amongst 

 the bases of the inner hair-cells, but 

 others are continued as fine threads 

 between the inner rods, and form a 

 second spiral band close to the outer 

 side of these and in contact with the 

 protoplasmic cell which ensheaths them. 

 Other fibres may be seen in sections to 

 pass across the tunnel of Corti between 

 the rods and to enter the region of the 

 outer hair-cells. Here the fibres, which 

 now again branch and alter their direc- 

 tion, run spirally parallel with the 

 successive series of hair-cells. They 

 rest against the corresponding cells of 

 Deiters, and in man form a bunch 

 of spirally-running fibres immediately 

 below the expanded part of each hair-cell (fig. 145). They form, therefore, altogether 

 five or six spiral strands of fibrils, which lie between the epithelium-cells of the organ 



