How the senses were studied

In 1851 Hermann von Helmholtz published a way to look through the pupil at the living retina, something no one had been able to do before.

A spot where nothing is seen

Looking inside the eye

For most of history no one could look at the back of a living eye. Hermann von Helmholtz, a German physician and physicist, solved the problem with an instrument he presented and published in 1851: the ophthalmoscope. It lit the inside of the eye so that the examiner could see the light coming back from the retina. Within a few years doctors were describing retinal conditions no one had seen in a living patient.

Light inside the eye is bent by several layers, and the lens changes shape, which makes the path of light very hard to calculate. Allvar Gullstrand, a Swedish eye doctor, solved it in about twenty years of work that began with his thesis of 1890. He received the 1911 Nobel Prize in Physiology or Medicine for his work on the dioptrics of the eye, meaning how the eye refracts light.

A new taste and the inner ear

In 1908 Kikunae Ikeda, a chemistry professor in Tokyo, set out to explain the taste of dashi, a broth made from kelp. He identified the key compound as a salt of glutamic acid and named its taste umami. OpenStax notes that umami was recognised as a fifth basic taste only in the mid-1980s, once research had shown how it is sensed.

Georg von Békésy, a Hungarian-born physicist, studied the cochlea and received the 1961 Nobel Prize for discovering the physical mechanism of stimulation within it. His experiments described how sound sets up a travelling wave along the basilar membrane, the picture you met in the lesson on ears.

Molecules for every sense

The Nobel Prize has followed the senses closely. In 1967 Ragnar Granit, Haldan Hartline and George Wald shared it for work on the chemistry and physiology of vision, and in 1981 David Hubel and Torsten Wiesel were honoured for how the brain processes visual information. Smell was one of the last senses to be explained. In 1991 Richard Axel and Linda Buck published the discovery of a large family of odorant receptor genes, and they received the 2004 prize. Temperature and touch came later still: David Julius identified the capsaicin receptor TRPV1 in 1997, Ardem Patapoutian identified the Piezo channels in 2010, and they shared the 2021 prize.

The 2021 Nobel summary begins with a much older idea. In the 17th century René Descartes imagined threads running from the skin to the brain, so that a foot near a flame would tug a thread. The threads turned out to be nerves, and the tug turned out to be ion channels opening in the membrane of a nerve ending. Many of the steps between those two pictures are in the timeline below.

This is educational material about how the body is built and works. It is not medical advice and is not for diagnosing or treating anyone.