THE CHEMISTRY OF DALTON,JOHN COLOR-BLINDNESS

John Dalton described his own color blindness in 1794. In common with his brother, he confused scarlet with green and pink with blue. Dalton supposed that his vitreous humor was tinted blue, selectively absorbi ng longer wavelengths. He instructed that his eyes should be examined after his death, but the examination revealed that the humors were per fectly clear. In experiments presented here, DNA extracted from his pr eserved eye tissue showed that Dalton was a deuteranope, lacking the m iddlewave photopigment of the retina. This diagnosis is shown to be co mpatible with the historical record of his phenotype, although it cont radicts Thomas Young's belief that Dalton was a protanope.