MELANISM, an excess of pigment in the skin and its appendages, producing real or com parative blackness; the opposite of albinism (q.v.). Melanism is less frequent than albinism, but more inclined to affect large numbers of individuals of a species, forming melanistic va rieties and is seen not only in man but in other mammals and in birds, reptiles, fishes, and in insects as, for example, certain moths which are found in Labrador and in the White Moun tains of New Hampshire, showing a possible connection between melanism and cold or high altitudes. Moisture is also considered to be a determining factor, as is indicated by the fact that the darkest races of men inhabit the warm est and dampest regions of the earth. A con spicuous example of melanism is afforded by the American squirrels, which are mel anistic varieties of species, especially the fox-squirrel (Sciurus nscier) and the gray squirrel (S. carolinensss). These varieties pre vail in certain parts of • the country, as the region of the Great Lakes and upper Mississippi Valley, and rarely occur elsewhere. Thus a black squirrel is almost unknown in New Eng land or the Hudson Valley, Another familiar example is found in the black leopards, which in a direct light seem absolutely black, but under reflected light betray a pattern of spots similar to those of the ordinary leopard. Such ex amples, as is the case with other melanistic animals, often occur in the same litter of young with normal forms. In many of the lower animals, as butterflies, melanistic tendencies are developed under certain conditions, especially of excessive moisture. The pigments in the
skin are mainly of the class called Melanins, which produce dark hues. Total abnormal melanism in man is unknown, but cases of partial melanism are on record. In one in stance one-half of the face was white, the other black A case is on record of a 16-year-old girl, a laundress, whose neck, face and upper chest became blue on certain occasions. She was otherwise apparently normal but the skin was so pigmented that when she blushed her color was blue instead of red, the change ap pearing with chameleonic rapidity and being associated with the accession of blood to the skin. A white towel was stained blue by being rubbed over her skin. Other cases of, skin discoloration are that of a man who became black in places and yellowish brown in others, and that of an unmarried woman white until she was 21 and thereafter black as a negro. The cause of this condition is unknown. Melano derma, chloasma, and liver-spots are terms ap plied to irregularly shaped yellow, brown and black colorations of the skin. Some of these spots are due to scratching following the bites of body-vermin, to prolonged pressure upon a portion of the skin, prolonged use internally of preparations of silver, to racial admixture, gen eral diseases, such as cancer or tuberculosis, etc. See CoLcaumn MATTERS ; COLORATION, Pao TECTIVE.