Jöns Jacob Berzelius is generally credited with providing the name “melanin” to the choroid coat of the eye. From him the substance known as melanin that is found “throughout the phylogenetic scale without any specific structural, biogenetic, or functional implication.”
But does Berzelius actually use the term “melanin?” On page 521 in volume 9 of his Lehrbuch der Chemie he starts his discussion on the choroid coat thusly:
“After we have known the outer clothing of the eyeball, I shall first give the contents of the selerotica, and afterwards the cornea. Choroidea The inner side of the selerotica is covered with its own black soft loose skin of the choroid or vascular membrane The blood vessels of the fetus, a soft, semi-transparent reddish matter, very similar to the brain mass of the fetus Of the optic nerve, and of the anatomists the”
On page 522 he continues:
“Retina, or retina. By means of the analysis of Lassaigne it has the same composition as the substance of the brain, but contains little fat, one part of which is phosphorous, and is not saponifiable, while the other consists of ordinary saponifiable fat Nervus opticus is richer in fat The retina should be 92 9 Water 6 25 Albumin and 0 85 Fat contain the nervus opticus only 70 36 Water but 22 07 Albumin and 4 40 unsaponifiable phosphorus grease In humans and monkeys which have round pupils they have in the rear In the middle of the eye, a bright yellow spot in the animals with elongated pupils occupies the inner part of the eye and forms the so-called “Tapetum lucidum”, which is greenish-white and shiny. On drying it becomes black, but after a period of many years it retains color. As soon as it is softened in water, when it passes from black through blue and dark green to light green. Where the bright part ends, the choroid is covered with a black color which covers the sides and the front part of the inner side of the larger sphere segment.
The black pigment of the eye lies loosely on the choroid, and can be easily removed. It is separated from other parts in such a way that, after the retina is removed, the choroid with the dye is removed from the selerotica into a fine linen flap, and so long In water as a black dye still slides in. It is retained in the water for a long time, and then appears dark brown, but can easily be filtered off and forms a black coherent mass on the substrate. This dye is from me and some years later by L Gmelin Examined the results of my investigation in brevity.
The result of my investigation was briefly the following. In both cold and boiling water, the dye is insoluble in alcohol, too, in nitric acid and hydrochloric acid, if diluted so as not to decompose it, as in concentrated acetic acid.”
