The difference of color in the human race is doubtless influenced by many causes, modifying the effect of position with regard to the tropics. The great elevation of a particular district, its proximity to the sea, the shades of a vast forest, the exhalations from extensive marshes, all tend to diminish materially the power of a southern sun.[210] On the other hand, intensity of heat is aggravated by the neighborhood of arid and sandy deserts, or rocky tracts. The action of long-continued heat creates a more permanent effect than the mere darkening of the outer skin: it alters the character of those subtile juices that display their color through the almost transparent covering.[211] We see that, from a constitutional peculiarity in individuals, the painful variety of the albino is sometimes produced in the hottest countries. Certain internal diseases, and different medicines, change the beautiful bloom of the young and healthy into repulsive and unnatural tints. A peculiar secretion of the carbon abounding in the human frame produces the jet black of the negro's skin, and enables him to bear without inconvenience the terrible sultriness of his native land.[212] The dark races, inferior in animal and intellectual powers to the white man, are yet nearly free from the deformities he so often exhibits, perhaps on account of a less susceptible and delicate structure. The Caucasian or European races, born and matured under a temperate climate, manifestly enjoy the highest gifts of man. Wherever they come in contact with their colored brother, he ultimately yields to the irresistible superiority, and becomes, according to the caprice of their haughty will, the victim, the dependent, or the slave.[213] There are other characteristics different from, but generally combined with color, which are influenced by constitutional varieties. The hair usually harmonizes with the complexion, and, like it, shows the influence of climate. In cold countries, the natural covering of every animal becomes rich and soft; the plentiful locks and manly beard of the European show a marked contrast to the coarse and scanty hair of the inhabitants of tropical countries. The development of mental power and refined habits of life have also a strong but slow effect upon the outward form.[214] Certain African nations of a higher intelligence and civilization than their rude neighbors, show much less of the peculiarities of the negro features. The refined Hindoo displays a delicate form and expression under his dark complexion. The black color and the negro features are accidentally not necessarily connected, and it seems to require both climate and inferiority of intellect to unite them in the same race.