Many have been the researches of anatomists respecting this black colour. Some pretend, that it is neither in the skin, nor in the epidermis, but in the cellular membrane which is between them; that this membrane, though washed, and held ever so long in warm water, does not change colour, while the skin, and the surface of the skin, appear to be nearly as white as those of other men. Dr. Town, in his letter to the Royal Society, and a few others, maintain, that the blood is black in negroes, and from which cause their colour originates; a fact which I am inclined to believe, from having remarked, that among ourselves the blood of those who are tawny, yellow, or brown, is proportionally more black than that of others. According to M. Barrere, this colour of the negroes is produced by the bile, which in them is not yellow, but always black as ink; of which he affirms he received certain proof from several negroes which he had occasion to dissect at Cayenne. When the bile is diffused, it tinges the skin of white people yellow; and it is probable, that if the former were black, the latter would be black also. But as when the overflow of the bile ceases, the skin recovers its natural whiteness, so on this principle there is a necessity for supposing that in the negroes there is always an overflow of bile, or at least that, as M. Barrere observes, it is so abundant, as naturally to secrete itself in the epidermis, in a quantity sufficient to communicate this black colour. It probable that the bile and blood of negroes are more brown than those of white men, as their skin is more black. But one of these facts can never be admitted as an explanation of the cause of the other; for if it is the blood or bile which, by its blackness, communicates this colour to the skin, then, instead of inquiring why the skin of negroes is black, we must inquire why their bile or blood is so; and thus, by deviating from the question, we find ourselves more than ever remote from the solution of it. For my own part, I own I have always been of opinion, that the cause which renders a Spaniard more brown than a Frenchman, and a Moor than a Spaniard, is also the cause which renders a Negro blacker than a Moor. At present I mean not to enquire how this cause acts, but only to ascertain that it does act, and that its effects are the more considerable, in proportion to the force and continuance of action.