Note 228 — APPENDIX. (continued 3)
Reading edition
According to the interesting researches of Mr. Gaultier, on the Organization of the Human Skin, p. 57. John Hunter observes, that in several animals, the coloration of the hair is independent of that of the skin.
Blumenbach informs us how climate operates in modifying the color of the skin. He states that the proximate cause of the dark color of the integuments in an abundance of carbon, secreted by the skin with hydrogen, precipitated and fixed in the rete mucosum by the contact of the atmospheric oxygen.—De Variet., p. 124.
If Voltaire is to be believed, no well-informed person formerly passed by Leyden without seeing a part of the black membrane (the reticulum mucosum) of a negro, dissected by the celebrated Ruysell. Their error is, however, now universally admitted. The "rete mucosum" has been discovered to be nothing but the latest layer of epidermis, the inner surface of which is being continually renewed as the exterior is worn away, just like the bark of a tree. There is no distinct coloring layer, it appears, either in the fair or the dark-skinned races, the peculiar hue of the latter depending upon the presence of coloring matter in the cells of the epidermis itself. Color, therefore, is not even skin deep, for it does not reach the true skin, being entirely confined to the epidermis or scarf skin.