The effort has been made to measure the colors of different peoples by a color scale. One such was devised by Broca, presenting over thirty shades, and another by Dr. Radde, in Germany; but on long journeys, or as furnished by different manufacturers, these scales undergo changes in the shades, so that they have not proved of the value anticipated.
As to the physiological cause of color, you know that the direct action of the sun on the skin is to stimulate the capillary action, and lead to an increased deposit of pigment, which we call “tan.” This pigment is largely carbon, a chemical element, principally excreted by the lungs in the form of carbonic oxide. When from any cause, such as a peculiar diet, or a congenital disproportion of lungs to liver, the carbonic oxide is less rapidly thrown off by the former organs, there will be an increased tendency to pigmentary deposit on the skin. This is visibly the fact in the African blacks, whose livers are larger in proportion to their lungs than in any other race.[11]
While all the truly black tribes dwell in or near the tropics, all the arctic dwellers are dark, as the Lapps, Samoyeds and Eskimos; therefore, it is not climate alone which has to do with the change. The Americans differ little in color among themselves from what part soever of the continent they come, and the Mongolians, though many have lived time immemorial in the cold and temperate zone, are never really white when of unmixed descent.
A practical scale for the colors of the skin is the following:
{ 1. Black. Dark. { 2. Dark brown, reddish undertone. { 3. Dark brown, yellowish undertone.
{ 1. Reddish. Medium. { { 2. Yellowish (olive).
{ 1. White, brown undertone (grayish). White. { 2. “ yellow undertone. { 3. “ rosy undertone.
The color of the _eyes_ should next have attention. Their hue is very characteristic of races and of families. Light eyes with dark skins are rare exceptions. Other things equal, they are lighter in men than in women. Extensive statistics have been collected in Europe to ascertain the prevalence of certain colors, and instructive results have been obtained.[12] The division usually adopted is into dark and light eyes.
{ 1. Light brown (hazel). Light eyes. { 2. Gray. { 3. Blue.