The pigment of the skin varies much in different persons within physiological limits. There is an absence of pigment from congenital defect (albinism), and a congenital excess (negrism). The pigment also varies in the same person at different times; it is often increased by exposure to the sun, by pregnancy (chloasma), etc. A peculiar form of pigmentation is that in Addison's disease, in which certain parts of the skin assume a bronzed colour. The excess of pigment here is not only in the rete Malpighii but in the papillae of the cutis and around the veins. This disease is associated with tuberculosis of the suprarenal capsules, but the connection of the local disease with the pigmentation of the skin is not very clear.