The spiral ganglion and the innervation of the human organ of Corti.

Five human cochleas were evaluated using the block surface method. The numbers of hair cells, nerve fibres in the osseous spiral lamina, and spiral ganglion cells were determined and correlated. The ultrastructural organization corresponds essentially to that of the mammalian ear, with the exception of multiple synaptic contacts of afferent nerve fibres with inner hair cells and surprisingly large numbers of outer spiral fibres.