Editing John Dalton (section)

=== Colour blindness ===
In 1794, shortly after his arrival in Manchester, Dalton was elected a member of the [[Manchester Literary and Philosophical Society]], the "Lit & Phil", and a few weeks later he communicated his first paper on "Extraordinary facts relating to the vision of colours", in which he postulated that shortage in colour perception was caused by discoloration of the liquid medium of the eyeball. As both he and his brother were [[Color blindness|colour blind]], he recognised that the condition must be hereditary.<ref name="daltoncb">{{Cite news |title=Life and work of John Dalton – Colour Blindness |url=http://news.bbc.co.uk/1/shared/spl/hi/pop_ups/03/sci_nat_the_life_and_work_of_john_dalton_(1766_1844)/html/4.stm |work=BBC News |access-date=9 November 2011 |archive-date=9 August 2017 |archive-url=https://web.archive.org/web/20170809043457/http://news.bbc.co.uk/1/shared/spl/hi/pop_ups/03/sci_nat_the_life_and_work_of_john_dalton_(1766_1844)/html/4.stm |url-status=live }}</ref>

Although Dalton's theory was later disproven, his early research into colour vision deficiency was recognized after his lifetime.{{efn |Dalton believed that his vitreous humour possessed an abnormal blue tint, causing his anomalous colour perception, and he gave instructions for his eyes to be examined on his death, to test this hypothesis. His wishes were duly carried out, but no blue colouration was found, and Dalton's hypothesis was refuted. The shrivelled remains of one eye have survived to this day, and now belong to the Manchester Literary and Philosophical Society."<ref>{{cite journal |doi=10.1136/bjo.82.2.203d |title=John Dalton's Colour Vision Legacy |journal=British Journal of Ophthalmology |volume=82 |issue=2 |pages=203d |year=1998 |last1=Regan |first1=B.|pmc=1722488 }}</ref>}} Examination of his preserved eyeball in 1995 demonstrated that Dalton had [[deuteranopia]], a type of [[congenital red-green color blindness]] in which the gene for medium wavelength sensitive (green) [[photopsin]]s is missing.<ref name="daltoncb" /> Individuals with this form of colour blindness see every colour as mapped to blue, yellow or gray, or, as Dalton wrote in his seminal paper,<ref>{{cite journal |last=Dalton |first=John |title=Extraordinary facts relating to the vision of colours: with observations |journal=Memoirs of the Literary and Philosophical Society of Manchester |year=1798 |volume=5 |pages=28–45 |url=https://catalog.hathitrust.org/Record/011812155 |access-date=8 August 2017 |archive-date=9 August 2017 |archive-url=https://web.archive.org/web/20170809042409/https://catalog.hathitrust.org/Record/011812155 |url-status=live }}</ref>

{{blockquote|That part of the image which others call red, appears to me little more than a shade, or defect of light; after that the orange, yellow and green seem one colour, which descends pretty uniformly from an intense to a rare yellow, making what I should call different shades of yellow.}}

{{multiple image
| align             = none
| image1            = Вечір на "інтегралі" - річка Південний Буг.jpg
| width1            = 300
| alt1              = A photograph of a river through the forest at sunset, with orange lichen-covered rocks in the foreground, a purple and yellowish pink sunset sky, a river reflecting the sky colors, and bright green trees and plants.
| caption1          = Normal vision
| image2            = Deuteranopia sight.jpg
| width2            = 300
| alt2              = The same photograph with its colors modified to simulate red–green color blindness. The orange areas of rocks, yellowish pink areas of the sky, and green plants now appear to have similar yellowish color, while purple parts of the sky and river look blue or gray.
| caption2          = Simulated red–green color blindness
| footer            = 
}}