r.oo 



Comparative Morphology of Chordates 



known as the organ of Corti (Fig. 517). This "organ" extends from 

 base to apex of the spiral. Its histologic elements include certain 

 curious rodlike cells (pillar cells or rods of Corti) arranged in parallel 

 series on either side of a "tunnel," their expanded bases resting upon 

 the basilar membrane (membrana basilaris) of the organ. At either- 

 side of the double row of pillar cells are the sensory cells, which are 

 short and do not extend down to the membrana basilaris. Each sensory 

 cell bears, on its free end, numerous fine stiff processes or "hairs" 

 which look like cilia but probably are not motile. In addition to the 

 pillar cells and "hair cells," the organ contains cells of several other 

 types, probably serving merely as supporting elements. The basilar 



Cochlear branch of tne acoustic nerve 



Fig. 515. Axial section of the cochlea of a cat. In the axis is the cochlear branch 

 of the acoustic nerve blackened by osrnic acid. Lateral branches of the nerve may 

 be traced to the spiral ganglions where the nerve-fibers arise. At the apex of the 

 cochlea is the helicotrema affording communication between the two perilymph 

 spaces (scalae). (dc) Ductus cochlearis; (set) scala tympani; (scv) scala vestibuli. 

 (X25.) (After Sobotta. Courtesy, Bremer- Weatherford: "Text-Book of His- 

 tology," Philadelphia, The Blakiston Company.) 



