The deviations from the natural color of the integuments are very numerous. They are, in general, either an absence of color or pallor; or a deepening of it; or with one or other of these may be combined a discoloration. Sometimes they are universal, at other times they are confined to larger or smaller tracts, or even to points, of the skin, in which case they are often almost peculiar to particular regions of the body. Their site may be the cutis vera, and their principal cause an anomaly in the quantity of blood circulating in its vessels, or rather a transient or permanent alteration in the constitution of the blood; or they may be situated in the epidermis, especially in the innermost - the Malpighian - layer of it, and may proceed either from the removal of the fibrin from the elementary cells of which the layer is composed, or from their containing an excessof fibrin, or some unusual pigment. Their cause is, in some cases, an anomaly in the constitution of the blood; in others it is some external influence affecting the skin during life: but in neither case is the mode in which the cause operates fully understood.

Lastly, all diseases of the texture of the skin are, of course, attended and followed by changes of its color.

Pallor, or change of the color to a variously tinted white, is observed during the lack of blood that succeeds hemorrhage and exhausting diseases; it occurs in dropsy, and in a very marked degree in cases of chlorosis. In Albinoes (Leucaethiopia) it is the result of a congenital deficiency of pigment, while in Achroma, the same defect is acquired. The latter condition may be seen in Negroes, and indeed in Europeans, wherever the surface is naturally dark-colored; as, for instance, at the parts of generation in either sex, where it appears in the form of white spots of various size, that gradually spread, and at last, in some few cases, amount to a general discoloring.

Yellow, either pure or mixed with green, is the well-known color in cases of icterus. A similar hue, but inclining to brown, arises from the deposit of pigment in the epidermis, either in small stains, or in large discolored tracts, or even over the whole surface of the body: the cause of this deposit is still partially obscure. The uniform embrowning of the skin, brought on in parts that are exposed especially to the light of the sun, is of this kind also; as well as the spotted stains of summer freckles (ephelis); and the liver spots (chloasma) which depend upon anomalies in the biliary system, and in the sexual system of the female. The color of the skin generally becomes dark, when with neglected it and indulgence in alcohol are combined infiltration of the liver with fat, and a tallowy state of the adipose substance, particularly of the subcutaneous layer of fat. The skin, in the last case, feels fatty, soft, and velvety, like that of a negro; its color proceeds from the deposition of a pigment containing fat in the deepest layer of the epidermis, - a fact of particular interest, on account of the combination, just mentioned, in which it stands.

Red coloring of the skin appears in extremely numerous forms, and with various shades of yellowish, bluish, livid, coppery, brown, and so on, which are well known as pathognomonic of various diseases. It occurs in cases of mere congestion, in inflammation, in exanthematous and impetiginous processes, in teleangiectasis and many of the diseases of the textures of the skin. The redness inclines to blue, and even to black, in hemorrhages into the cutaneous tissue, or upon its surface, in sugillations, ecchymosis, vibices, petechiae, etc.

In cases of cyanosis there is a general bluish or blue color of the integuments; but it is principally marked in situations where the skin is delicate and highly vascular, and in the extremities. The blue tint, when limited to certain spots, is a result of local congestion. A transient blue-ness of the skin has also been noticed, in a few cases, at various parts of the surface, but its internal cause is unknown (Otto).

Spots (livores) of a bluish-red, a livid, or a blackish-blue color, appear upon the body soon after death.

Various shades of bronze are produced upon the skin by the long-continued use of nitrate of silver: they sometimes gradually disappear, but occasionally they remain permanently. No evidence has yet been obtained as to the seat of this discoloring: it appears first, and has its deepest hue, on parts of the body which are exposed to light.

A black color is observed principally in old cachectic persons, in whom it is sometimes diffuse and extends over large tracts of skin, especially in the lower limbs, and sometimes appears in the form of black nodules, which are deposited chiefly on the face. It has in a few cases been seen gradually spreading over the whole body. It is named melasma, and is a different affection from cancer melanodes of the skin.

Almost all these discolorings occur also, as congenital and partial appearances, in the various naevi.

A tawny color, a dirty gray, a dirty bluish, a leaden hue is by far the most frequent of all the changes in the color of the skin: it is an expression of dyscrasia, and of faulty chymification, and is found in the course of acute and chronic diseases.