Quantitative analysis of the innervation of the chicken basilar papilla.

Unlike the organ of Corti in mammals, the avian basilar papilla has no distinct populations of hair cells. Instead, there is a continuous change between the extreme forms (tall hair cells = THC, and short hair cells = SHC). The hair-cell innervation pattern is complicated, there being no simple gradient between THC (mainly innervated by afferent fibers) and SHC (mainly innervated by efferent fibers). In the basal half of the papilla, SHC have only efferent innervation. The lack of afferent innervation indicates that the function of basal SHC is restricted to the basilar papilla itself, perhaps modifying its mechanical properties.