Abstract
The efferent innervation of the inner hair cells in Corti's organ of the laboratory rat and of a bat was investigated with help of histochemical staining of the inner spiral bundle. The area of acetylcholinesterase-positive fibres in the inner spiral bundle regions was measured. The bulk of the efferent fibres lie in the middle part of the cochlea. Towards the apical and lower basal turns a distinct decrease in the number of fibres was observed.