Visionary of Colour

Ragnar Granit, a Finnish-Swedish physiologist, was born on this day in Helsinki in 1900. He received the Nobel Prize in Physiology or Medicine, along with George Wald and Haldan Hartline, for his discoveries concerning colour vision and other processes in the eye. By attaching microelectrodes to individual cells in the retina – a light-sensitive nerve net lining the inner surface of the eye – he demonstrated that light not only simulates, but also inhibits, impulses shooting along the optic nerve to the brain. He also showed that to have colour vision, some eye receptor cells are sensitive to the whole spectrum, and so are not colour specific, while others respond to a much narrower band, only reacting to particular colours. Here’s a scanning electron micrograph of the fovea, the area in the retina that contains only receptor cells and produces the sharpest image in the brain.

Written by Nick Kennedy

• Image by P. Motta
• Sapienza Università di Roma, Italy
• Any re-use of this image must be authorised by Science Photo Library