As a generic term, the name melanin is applied not only to the true melanin, but to any black pigment which results from the oxidation of isocyclic or heterocyclic hydroxy compounds, or from the oxidation of the hydrolysates of proteins. The term in the extreme sense may even be applied to the black substance that is formed by boiling dextrose and urea together in strong hydrochloric acid.<sup>1</sup>The artificial type of melanin is perhaps properly called humin.<sup>2</sup>Melanin, as a specific term, is considered to designate the dark insoluble pigment which occurs normally or pathologically in the organism.<sup>3</sup>It may be found in the coloring matter of the hair, skin, feathers, horn and eyes of vertebrates, as well as in other animal and plant tissues. Apparently, there is a chemical relationship between the artificial melanin, or humin, and the natural melanin, although this relationship has not