THE INTERNAL EAR, OR LABYRINTH 



1147 



the canal of the ductus cochlearis and appears as a ridge (crista spiralis), winding 

 spirally throughout the whole length of the ductus cochlearis. It is seen to be com- 

 posed of a remarkable arrangement of cells, which may be likened to the. keyboard 

 of a piano. Of these cells, the central ones are rod-like bodies and are called the 

 inner and outer rods of Corti. Thfir bases are expanded and placed on the basilar 



Membrana tectoria. 



Outer hair cells. 



Limbns. 



*uv 



Cells of Deiters. 

 Outer rod. 

 Basilar membrane. 

 FIG. 856. Section through the organ of Corti. Magnified. (G. Retzius.) 



Nerve fibres. 



membrane, at some little distance from each other, while their intermediate por- 

 tions are inclined toward each other, so as to meet at their opposite extremities, 

 and form a series of arches roofing over a minute tunnel, the canal or tunnel of 

 Corti, between them and the basilar membrane which ascends spirally through 

 the whole length of the cochlea. 



INTERNAL AUDI- 

 TORY CELLS 



BASILAR MEMBRANE 



FIG. 857. Organ of Corti. Diagrammatic view of a small portion. (Testut.) 



The inner rods (Fig. 856), some 6000 in number, are more numerous than the 

 outer ones, and rest on the basilar membrane, close to the labium tympanicum; 

 they project obliquely upward and outward, and terminate above in expanded 

 extremities which resemble in shape the upper end of the ulna, with its sigmoid 

 cavity, coronoid and olecranon processes. On the outer side of the rod, in the 



