THE COLOR OF RED HAIR 783 from kwashiorkor, a severe nutritional deficiency (19). That redness does not necessarily presuppose an iron pigment is proved by the Irish setter whose red hair contains no trichosiderin. Although two pigmentary pathways must be postulated, there is no reason why these pathways must follow a common initial course, as sug- gested by Fitzpatrick et al. (2). All the available facts may be explained by assuming two coexisting but independent pathways for red and black pigments. Another unsolved problem is presented by the "missing links" be- tween chicken and man. Trichosiderin may occur in other species as well, but as yet none has been found. Red-haired individuals may be biologically inferior. The hair cover- ing the entire body of our ancestors regardless of its color, offered ade- quate protection against ultraviolet light. As hair became a rudimen- tary structure, the epidermis became exposed to sun against which the iron pigment apparently does not offer adequate protection. The pres- ent scarcity of red-haired people may be due to their suppression by the more viable dark-colored races. Discovery of a previously unknown substance, such as the iron pig- ment of red hair, always raises more questions than can be answered. Most of these problems are accessible to experimental study. It is hoped that their solution will be attempted before another 25 years will elapse. (Received February 3, 1967) REFERENCES (1) Wertz, J. E., et al., Electron Spin Resonance Studies of Antoxidation of $,4-dihydroxy- phenylalanine, in Blois, M. S., Jr., et al., Free Radicals in Biological Systems, Academic Press, New York, N.Y., 1961, pp. 183-193. (2) Fitzpatrick, T. B., et al., ]'he Nature of Hair Pigment, in Montagna, W., and Ellis, R. A., Biology of Hair Growth, Academic Press, New York, N.Y., 1958, pp. 255-301. (3) Fitzpatrick, T. B., Personal communication. (4) Sorby, H. C., On the colouring matters found in human hair, J. Anthropol. Inst. Gt. Brit., 8, 1-14 (January 1878). '(5) Fleseh, P., and Rothman, S., Isolation of an iron pigment from human red hair, J. Invest. Dermatol., 6,257-270 (August 1945). (6) Rothman, S., and Fleseh, P., Isolation of an iron pigment from human red hair, Proc. Soc. Exptl. Biol. Med., 53, 134-135 (June 1943). (7) Hanna, B. L., Production of pigments similar to those from hair from amino acid and keratin interaction, Ibid., 80, 28•-287 (June 1952). (8) Rothman, S., Physiology and Biochemistry of the Skin, The University of Chicago Press, Chicago, II1., 1954, pp. 518-519. (9) Nickerson, N., Relation between black and red melanin pigments in feathers, Physiol. Zool., 19, 66-77 (January 1946).

784 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS (10) Smyth, J. R., Porter, J. W., and Bohren, B. B., A study of pigments from red, brown and buff feathers and hair, Physiol. Zool., 24,205-216 (July 1951). (11) Barnicot, N. A.., The pigment, trichosiderin, from human red hair, Nature, 177, 528-529 (Mar. 17, 1956). (12) Flesch, P., Esoda, E. J. and Katz, S. A., The iron pigment of red hair and feathers, J. Invest. Dermatol., 47, 595-597 (December 1966). (13) Dutcher, T. F., and Rothman, S., Iron, copper, and ash content of human hair of dif- ferent colors, Ibid., 17, 65-68 (Aug. 1951). (14) Lowry, O. H., Rosebrough, N.J., lCarr, A. L., and Randall, R. J., Protein measurement with the Folin phenol reagent, J. Biol. Chem., 193,265-275 (November 1951). (15) Rothman, S., and Flesch, P., Isolation of an iron pigment from human red hair, Proc. Soc. Exptl. Biol. Med., 53, 134-135 (May-June 1943). (16) Fox, H. M., and Vevers, G., The Nature of Animal Colours, Sidgwick and Jackson Ltd., London, 1960, p. 33. (17) Bohren, B. B., Conrad, R. M., and Warren, D.C., A chemical and histological study of the feather pigments of the domestic fowl, Am. Naturalist, 77, 481-518 (November- December 1943). (18) Barnicot, N. A., and Birbeck, M. S.C., The Electron Microscopy of Human Melanocytes and Melanin Granules, in Montagna, W., and Ellis, R. A., Biology of Hair Growth, Academic Press, New York, N.Y., 1958, pp. 255-301. (19) El-Hefnawi, H., Shukri, A. S., and Rasheed, A., Kwashiorkor in the United Arab Re- public, Brit..1. Dermatol., 77, 137-150 (March 1965).