"In the present state of our knowledge we can only say that it seems highly probable that the pigment of the negro's hair is not different from the dark pigment found in the hair of the white races, and we may infer that the pigment of the black skin differs only in amount and not in kind from that deposited in the skin of the white man" (p. 400). Digital facsimile from PubMedCentral at this link.