In those climates alone, then, where circumstances combine to create a constant and excessive heat, do we meet with negroes. This heat is necessary not only to the production, but even to the preservation of negroes; and where the heat, though violent, is not comparable to that of Senegal, the negro infants are so susceptible of the impressions of the air, that there is a necessity for keeping them during the first nine days in warm apartments; if this precaution is omitted, and they are exposed to the air soon after their birth, a convulsion in the jaw succeeds, which preventing them from receiving any sustenance, they presently die. In the History of the Academy of Sciences we read, that M. Littre, in dissecting a negro, in 1702, remarked, that the point of the glands which was not covered with the prepuce was black, and the rest perfectly white. From this observation it is evident, that the air is necessary to produce the blackness of negroes. Their children are born white, or rather red, like those of other men, but two or three days after they change to a tawny yellow, which gradually darkens till the seventh or eighth day, when they are completely black. All children two or three days after their birth have a kind of jaundice, which in white children is transitory, and leaves no impression upon the skin; but in negro children it gives a colour to the skin, and continues to grow more and more black. M. Kolbe mentions having observed this fact among the children of Hottentots. This jaundice, however, and the impression of the air, seem to be only occasional, and not the primary cause of this blackness; since it is remarked, that the children of negroes have, the instant of their birth, a blackness in the genitals, and at the root of the nails. The action of the air and the jaundice may serve to extend this blackness, but it is certain that the principle of it is communicated to the children by their parents; that in whatever country a negro may be born, he will be as black as if he had been brought forth in his own; and if there is any difference in the first generation it is imperceptible; from this circumstance, however, we are not to suppose, that after a certain number of generations, the colour would not undergo a very sensible change.