And the colours of horns and nails and claw and hoof follow the
colour of the skin and the hair. For according as the skin of an
animal is black, or white, or of medium hue, so are the horns, the
claws, or the hooves, as the case may be, of hue to match. And it is
the same with nails. The teeth, however, follow after the bones.
Thus in black men, such as the Aethiopians and the like, the teeth and
bones are white, but the nails are black, like the whole of the skin.