is not more inconsistent with the operations of nature than with the principles of genuine philosophy.

But the question still returns: whence, then, proceed those astonishing diversities among the different nations of mankind, upon which the arrangement now offered is founded?

The answer is, that they are the effect of a combination of causes: some of which are obvious, others of which must be conjectured, and a few of which are beyond the reach of human comprehension: but all of which are common to other animals, as well as to man; for extraordinary as these diversities may appear, they are equally to be met with in the varieties of several other kinds of animals that can be proved to have been produced from a single species, and, in one or two instances, from a single pair.

The chief causes we are acquainted with are the four following: climate, food, manner of life, and hereditary diseases.

I. The influence which CLIMATE principally produces on the animal frame is on the color of the skin and on the extent of the stature. All the deepest colors we are acquainted with are those of hot climates; and all the lightest those of cold ones. In our own country we perceive daily, that an exposure to the rays of the sun turns the skin from its natural whiteness to a deep brown or tan; and that à seclusion from the sun keeps it fair and unfreckled. In like manner the tree-frog (rana arborea) while living in the shade is of a light yellow, but of a dark green when he is obliged to shift from the shade into the sunshine. So the nereis lacustris, though whitish under the darkness of a projecting bank, is red when exposed to the sun's rays. And that the larves of most insects that burrow in the cavities of the earth, of plants, or of animals, are white, from the same cause, is clear, since being confined under glasses that admit the influence of solar light, they exchange their whiteness for a brownish hue.

The same remark will apply to plants as well as to animals; and hence nothing more is necessary to bleach or whiten them, than to exclude them from the light of day. Hence the birds, beasts, flowers, and even fishes of the equatorial regions are uniformly brighter or deeper tinctured in their spots, their feathers, their petals, and their scales, than we find them in any other part of the world. And hence, one reason at least for the deep jet which, for the most part, prevails among mankind under the equator; the dark-brown and copper colors found under the tropics; and the olive, shifting through every intermediate shade to the fair and sanguine complexion, as

reason why the Asiatic and African women, confined to the walls of their seraglios, are as white as Europeans; why Moorish children, of both sexes, are, at first, equally fair, and why the fairness continues among the girls, but is soon lost among the boys.

As we approach the poles, on the contrary, we find every thing progressively whiten; bears, foxes, hares, falcons, crows, and blackbirds, all assume the same common livery; while many of them change their color with the change of the season itself. For the same reason, as also because they have a thinner mucous web, the Abyssinians are less deep in color than the negro race; for though their geographical climate is nearly the same, their physical climate differs essentially: the country stands much higher, and its temperature is far lower.

The immediate matter of color, as I had occasion to observe more fully in a preceding lecture, is the mucous pigment which forms the middle layer of the general integument of the skin; and upon this the sun, in hot climates, appears to act in a twofold manner; first, by the direct affinity of its colorific rays with the oxygen of the animal surface, in consequence of which the oxygen is detached and flies off; and the carbon and hydrogen being set at liberty, form a more or less perfect charcoal according to the nature of their union; and next, by the indirect influence which its calorific rays, like many other stimulants, produce upon the liver, by exciting it to a secretion of more abundant bile, and of a deeper hue. I have formerly remarked that this second or coloring layer of the general integument of the skin, differs (as indeed all the layers of the skin do) in its thickness, not only in different kinds of animals, but very frequently in different species, varieties, and even individuals. Thus in our own country we find it more abundant in some persons than in others; and wherever it is most abundant, we find the complexion also of a darker and coarser and greasier appearance, upon a common exposure to the solar light and heat: and we find also, that the hair is almost uniformly influenced by such increase of color, and is proportionally coarser and darker.

It is of some consequence to attend to this observation; for it may serve to explain a physiological fact that has hitherto been supposed of difficult elucidation.

A certain degree of heat, though less than that of the tropics, appears favorable to increase of stature; and I have already observed, that the tallest tribes we are acquainted with are situated at the back of Cape Horn, and the Cape of Good Hope. On the contrary, the

most diminutive we are acquainted with are those that inhabit the coldest regions or the highest mountains in the world: such are the Laplanders and Nova Zemblians in Europe, the Samoieds, Ostiacs, and Tungooses in Asia, and the Greenlanders and Esquimaux in America. Such, too, are the Kimos of Madagascar, if the account of these pigmy people may be depended upon, whose native region is stated to be the central and highest tracts of the island, forming, according to Commerson, an elevation of not less than sixteen or eighteen hundred fathoms above the level of the sea.

A multitude of distinct tribes have of late years been discovered in the interior of Africa, in the midst of the black tribes, exhibiting nothing more than a red or copper hue, with lank black hair. And, in like manner, around the banks of the lower Orinoco, in Mexico, where the climate is much hotter, there are many clans of a much lighter hue than those around the banks of the Rio Negro, where it is much cooler; and M. Humboldt has hence ventured to assert that we have here a full proof that climate produces no effect upon the color of the skin. Such an assertion, however, is far too hasty; for he should first have shown that the thickness of the mucous web or coloring material is equally abundant in all these instances. For if it be more abundant (as it probably is) in the tribes that are swarthiest, we have reason to expect that a swarthier color will be found where there is an equal or even a less exposure to solar light and heat; and we well know that the hair will vary in proportion.*

II. The effects of DIFFERENT KINDS OF FOOD upon the animal system are as extensive and as wonderful as those of different climates. The fineness and coarseness of the wool or hair, the firmness and flavor of the flesh, and in some degree the color of the skin, and extent of the stature, are all influenced by the nature of the diet. Oils and spirits produce a peculiar excitement of the liver; and like the calorific rays of the sun, usually become the means of throwing an overcharge of bile into the circulation. Hence the sallow and olive hue of many who unduly addict themselves to vinous potation, and who at the same time make use of but little exercise. And hence also the dark and dingy color of the pigmy people inhabiting high northern latitudes, to whom we have just adverted, and whose usual diet consists of fish and other oils, often rancied and offensive. Though it must be admitted that this color is in most instances aid

*See Essai Politique sur la Nauvelle Espagne, par Alexander de Humboldt, &c.

ed by the clouds of smoke in which they sit constantly involved in their wretched cabins, and the filth and grease with which they often besmear their skins. And hence, also, one cause of their diminutive stature; the food they feed on being unassimilating and innutrative. Swine and all other animals fed on madder-root, or that of gallium verum, or yellow-ladies-bed-straw, have the bones themselves tinged of a deep red, or yellow: and M. Huber of Lausanne, who has of late years made so many valuable discoveries in the natural habits of the honey-bee, has proved himself able by a difference in the food alone, as indeed Debraw had done long before him,* to convert what is commonly, but improperly, called a neuter into a queen bee.

III. It would be superfluous to dwell on the changes of body and perceptive powers produced in the animal system by a DIFFERENCE IN THE MANNERS AND CUSTOMS. We have the most striking proofs of this effect in all the domestic animals by which we are surrounded. Compare the wild horse with the disciplined; the bison with the ox, which last is usually regarded as the bison in a state of tameness; and the Siberian argali with the sheep which is said to have sprung from it. Compare the modern Romans with the ancient; the low cunning and servile temper of too many of the Greek tribes of the present day, that still bend to and kiss the Ottoman rod, with the noble courage and patriotic enthusiasm of their forefathers, who drove back the tyrant of Persia, and his million of men, across the Hellespont, and dashed to pieces the proud bridge with which he boasted of having conquered the billows.

It is in reality from long and deeply rooted habit alone that the black, red, and olive color of the Ethiopian, American, and Moguls is continued in the future lineage for so many generations after their removal into other parts of the world; and that nothing will, in general, restore the skin to its original fairness but a long succession of intermixtures with the European variety. It is a singular circumstance that the black color appears to form a less permanent habit than the red or olive; or, in other words, the color chiefly produced by the action of the sun's colorific rays, than that produced by the action of its calorific rays: for the children of olive and copper-colored parents exhibit the parental hue from the moment of birth; but in those of blacks it is usually six, eight, or ten months before the black pigment is fully secreted. We also sometimes find this not secreted at all,

* See Phil. Trans. for 1777, p. 15.

whence the anomaly of white negroes; and sometimes only in interrupted lines or patches, whence the anomaly of spotted negroes; and we have even a few rare cases of negroes in America who, in consequence of very severe illness, have had the whole of the black pigment absorbed and carried off, and a white pigment diffused in its stead. In other words, we have instances of a black man being suddenly bleached into a white man. These instances are indeed of rare occurrence; but they are sufficient to show the absurdity of the argument for a plurality of human stocks or species, from a mere difference in the color of the skin; an argument thus proved to be altogether superficial, and which we may gravely assert to be not more than skin-deep.

It is in consequence of this power in the system, of secreting a dark colored pigment under particular circumstances, that we not unfrequently see the skin of a very fair woman, when in a state of pregnancy, changed to a deep tawny, and almost to a black; and it is hence that the black pigment of the eye is perpetually maintained and replenished.*

Dr. Wells gave a paper to the Royal Society, which was read April 1, 1813, containing an account of a woman (Harriet Tresh) "whose left shoulder, arm and hand are as black as the blackest African's, while all the rest of the skin is very white. She is a native of Sussex, and the cause she assigns is, that her mother set her foot upon a lobster during her pregnancy." So that we have not only instances of blacks being suddenly bleached, but of whites being made more or less black. In like manner, confined birds sometimes become wholly black; and are said to become so occasionally in the course of a single night. So the male kestrel, from being barred on the tail feathers, becomes wholly ash-colored except at the end; and the heron, gull, and others whose tail is white when matured, are for the first two years mottled.

IV. But it is probable that a very great part of the more striking distinctions we have noticed, and almost all the subordinate variations occasionally to be met with, are the result of a MORBID AND HEREDITARY AFFECTION. The vast influence which this recondite but active cause possesses over both the body and the mind are known in some degree to every one from facts that are daily presenting themselves to us. We see gout, consumption, scrofula, leprosy, propagated on various occasions, and madness and fatuity and hypochondriacal affec