Macula

(mak'-u-lah). A spot or discoloration of the skin, not elevated above the surrounding level. It may be of various sizes, shapes, and tints, and is due to hyperemia, to extravasation of blood and blood coloring-matter, to dilatation of the cutaneous ve els, or to changes in the pigmentation of the skin. M. acusticae, the terminations of the auditory nerve in the saccule and utricle. M. albida, leukoderma. M. artificial is, a spot produced artificially in order to deceive. M. aurea, the central fovea of the retina. M., Cerebral. See T M. cerule a, a dark spot occurring on a skin infested with parasites. M. corneae arcuata, the arcus senilis. M. cribrosa, a name given to the perforations of the fovea hemispheric a for the pa age of the filaments of the auditory nerve. M. flava. See M. lulea. M. folliculi, the stigma of the Graafian vesicle. M. fusc a, a spot due to diseases characterized by pigmentation, as lentigo and chloasma. M., Germinal, the small spot constituting the germinal vesicle or nucleus of the ovum. M. hepatica, a liver-spot, including pigmentary spots due to various diseases. M. lat a platen, an obscure disease of the skin, sometimes epidemic, characterized by burning, red spots and pustulation. M. lenticular is, a lenticular spot; the roseola of typhoid fever. M. livid a, a hemorrhagic or purpuric spot. M. lutea, the yellow spot of the retina, called, sometimes, the spot of So emmer ing, but usually called simply the macula. The depre ion in its center is called the fovea central is. Itis the point of clearest vision and is pierced by the visual axis. M. materna, birth-mark, or nevus. M. nigra, a disease of the skin a ociated with very dark spots of pigmentation. M. ocular is, the eye-spot of the Protozoa, Cnidaria, Platodes, and Crustacea. M., Roberts', a heaping up of pigment in a part of a red corpuscle when a dilute solution of tannic acid is added to the blood. M. Solaris, a freckle. M. syphilitic a, the copper' stain of the skin left by a syphiloderm.