208 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS As concerns trace metals, copper deficiency in animals has been most prominently associated with defective melanin formation. 4o,4• Our knowledge about neural factors which may be involved in controlling melanin formation is very incomplete. Clinically, however, disorders of pigmentation such as hyperpigmentation and depigmentation are at times localized along the patterns of distribution of cutaneous nerves. 4-ø Sunlight irradiation brings about darkening of the skin through several mechanisms worthy of comment. An initial darkening effect often appears a few minutes after exposure and reaches a maximum within one hour. 4• This phenomenon is brought about by the relatively long-wave ultra- violet spectrum between 300 and 420 m/• with a maximally effective wave- length of 340 m/•. This pigment darkening effect is believed to result from photo-oxidation of preformed, relatively reduced melanin. It is abolished if the oxygen supply to the skin is cut off. A second effect occurs several days after sunlight exposure, and consists of an upward migration of melanin granules in the epidermis, 44 probably as a result of dispersion of these granules within the dendritic melanocytes. Finally, a third most important factor in sun-tanning is the new formation of melanin. • This begins after two days and reaches a maximum after about 19 days. After one month the amount of newly formed melanin begins to decline, and after 9 to 10 months the melanin content of the skin is almost back to normal. This new formation of melanin is caused by the shorter- wave-length erythema-producing ultraviolet spectrum between 280 and 310 mt•. It is of interest to point out that many sun-screening preparations, especially those based on para-aminobenzoic acid, effectively filter out these erythema wave-lengths of sunlight, yet permit the passage of pigment- darkening rays above 320 m/•. This well explains the failure of such prepara- tions to protect against the darkening effect of sunlight on freckles. It is not correct, however, to claim that such sun-screening preparations permit sun-tanning while eliminating the erythema wave-lengths of sunlight, because such erythema wave-lengths are actually required for the new formation of melanin. Finally, I would like to say a few words about the pigment of red hair. In the past it was believed that hair color, whether brown, red, blond or black depended only on the number, size, and dispersion or state of oxidation of ordinary melanin granules in which pigment derived only from tyrosine. Very recently Fitzpatrick has found evidence that tryptophane may repre- sent an important precursor of human red hair pigment. 45 The pigment granules in human red hair differ morphologically from the granules in dark hair in being smaller and more finely granulated in structure. Also, a special, iron-containing pigment, trichosiderin, 40 has been extracted only from red hair. Furthermore, a peculiar chloroquine induced loss of hair pigment which is sometimes observed clinically seems to occur exclusively

SKIN AND HAIR PIGMENTATION 209 in individuals with red or strawberry blond hair. Therefore, there is good reason to suspect that red hair pigment formation involves biochemical pathways other than just the tyrosinase-tyrosine reaction. In closing, it is amusing to speculate rather wildly about the possibility that the greater temperamentality popularly supposed to be associated with red hair might perhaps some day actually find a basis in a biochemical difference in trypto- phane metabolism in such individuals, since tryptophane is also the source of 5-hydroxytryptarnine, which has important roles in brain function as revealed by modern psychopharmacologic studies. [Received: 31st December 1957] REFERENCES* Edwards, E. A., and Duntley, S.Q. Arner. J. zinat., 1939, 6õ, 1-33. Edwards, E. A., Hamilton, J. B., Duntley, S. Q., and Hubert, G. 2•ndocrinology, 1941, gS, 119-28. Hall, T. C., McCracken, B. H., and Thorn, G.W.J. clin. 2•ndocrin., 1953, 18, 243-57. Jesionek, A. Biologic der gesunden und kranken Haut, 1916. (Leipzig: F. C. W. Vogel.) Sumner, F.B. Cited by Lorus, J., and Milne, M.J. Sci. Arner., 1952, 186, 64-7. Eppinger, H. Biochem. Z., 1910, gS, 181-92. Becker, S. W., Jr., Fitzpatrick, T. B., and Montgomery, H. Arch. Derrn. Syph., N.Y., 1952, õõ, 511-23. Taylor, A.C.J. exp. Zool., 1949, 110, 77-112. Liebow, A. A., Warren, S., and De Coursey, E. Arner. J. Path., 1949, gõ, 853-1027. Masson, P., Miner, R. W. (ed.). The biology of melanornas, 1948, 15-51, "Special . publications of the New York Academy of Sciences," 4. (New York: The Academy.) - Billingham, R. E., and Medawar, P. B. Phil. Trans., 1953, g37, 151-71. Birbeck, M. S.C. •/he Electron Microscopy of the Melanocyte and the Spread of Pigrnent. 1957 Symposium on The Biology of Hair Growth, London. (To be published.) Mason, H. S., Kahler, H., MacCardle, R. C., and Dalton, A. J. Proc. Soc. exp. Biol., N.Y., 1947, õõ, 421-31. Greenstein, J. P., Turner, F. C., and Jenrette, W. V. J. nat. Cancer Inst., 1940, 1, 377-85. Raper, H.S. Physiol. Rev., 1928, 8,245-82. Lerner, A. B., Fitzpatrick, T. B., Calkins, E. and Summerson, W. H. J. Biol. Chern., 1949, 178, 185-95 1950, 187, 793-802 and 1951, 1Ol, 799-806. Lerner, A. B. Arner. J. Me, d., 1955, 19,902-24. Wilkinson, J. F., and Ashford, C.A. Lancet, 1936, •, 967-70. Rothman, S., Krysa, H. F., and Smiljanic, A.M. Proc. Soc. exp. Biol., N.Y., 1946, 6g, 208-9. Fitzpatrick, T. B., Becker, S. W., Jr., Lerner, A. B., and Montgomery, H. Science, 1950, 11•, 223-25. Magnin, P. H., and Rothman, S. Dermatologica, Basel, 1957, 115, 315-320. Miyamoto, M., and Fitzpatrick, T. B. Nature, Lond., 1957, 179, 199-200. Oliver, E. A., Schwartz, L., and Warren. L. H. •trch. Derrn. Syph., N.Y., 1940, 993-1014. Harris, J. I., and Lerner, A.B. ivature, Lond., 1957, 179, 1346-7. Lerner, A. B., and Lee, T.H.y. •trner. chern. Soc., 1955, 77, 1066-7. Lee, T. H., and Lerner, A.B.J. biol. Chern., 1956, ggl, 943-959. Geschwind, I. I., Li, C. H., and Barnaft, L. J. Amer. chern. Soc., 1956, 78, 4494-5. Geschwind, I. I., Li, C. H., and Barnaft, L. J. Arner. chern. Soc., 1957, 79, 620-25. Lerner, A. B., Shizume, K., and Fitzpatrick, T. B. J. inoest. Derrn., 1953, gl, 337-8. Frieden, E. H., and Bozer, J.M. Proc. Soc. exp. Biol., 1V.Y., 1951, ??, 35-7. Lynn, W. G., and De Marie, A. Science, 1946, 104, 31. Trinkaus, J.P. Gordon, M. (ed.). Pigment cell growth, 1953, 73-92. (New York: Academic Press, Inc.) Davis, M. E., Boynton, M. W., Ferguson, J. H., and Rothman, S. J. clin. 2•ndocrin, 1945, õ, 138-46. Pfeiffer, C. A., Hooker, C. W., and Kirschbaum, A. Endocrinology, 1944, •4, 389-99.