It was a coincidence. John Dalton, the famous English naturalist and chemist, was wrong. Everyone knew he was dressed very formally (he was a very traditional Quaker). When they saw him walking around in fiery red stockings, they let them know. He replied that he saw her gray. So the discoverer of color blindness realized his vision problem and decided to investigate it. In 1794 he presented an essay on this. Today it is also known as dyschromatopsia.
What about the color blind?
Our eyes contain two types of photoreceptors that are responsible for seeing. The swabs help us see in low light. However, they do not provide any information about the color. The cones work when there is plenty of light. They divide the world into three colors: blue, green and red. Color blind people often lack one of three types of cones. That’s why they only see some colors. People who have no cones and consequently see no color at all are called acromas. The genetic defect is hereditary.
This was totally unknown in Dalton’s time. He believed that the causes of his defect were based on the physical laws of optics. He assumed that the vitreous humor in his eyes would not be transparent like a normal eye. He thought it was blue and maybe it would work as a filter for red.
There was, of course, no way to prove it unless he took his eyes out. That’s why he put it in his will. He poked his eyes out to see if the vitreous was bluish. The day after her death, her family doctor Joseph Ransome removed the vitreous humor from her eyes. But it was completely transparent.
The color-blind hypothesis that color blindness was due to a “pretinal filter” was rejected. Ransome put his eyes in a container. This happened to be guarded with pride by the Philosophical and Literary Society of Manchester.
The story wasn’t over yet
In 1983 the biochemist Kary Mullis developed a new molecular biological technique: PCR. A small nucleic acid fragment can be cloned multiple times to obtain sequential copies. It became very popular after Mullis won the 1993 Nobel Prize in Chemistry.
The second century of Dalton’s attempt at sight was celebrated in 1994. A group of English geneticists and ophthalmologists asked the Manchester Society for permission to take a small sample of Dalton’s retina. They wanted to amplify the DNA using the PCR technique to study the genes. It turned out that Dalton had the gene for the red photopigment, but the homologue for the green photopigment was missing. Dalton was actually a “deuteranope” who sees the red part of the spectrum darker.
The discoverer of color blindness knew what he was doing when he surrendered his eyes to science. He knew that sooner or later someone would explain why I was wearing outrageous red stockings instead of the gray ones he saw.
