Hensen, Viktor (1835–1924), German physiologist and marine biologist. Hensen did basic research on the physiology of hearing and sight in humans and in lower animals as well. In 1863 he studied the morphology of the human cochlea and described the cells now known as the cells of Hensen. He also discovered that the fibers of the cochlear basilar membrane are resonant corpuscles capable of vibrating. In his examination of human sight he studied the dispersion of cones in the center of the retina. In the lower animals he investigated the organs of hearing in grasshoppers, decapods, and various fishes. His companion interest in marine biology led to an investigation of plankton (he was the first to use the term plankton) as well as of fishes.