22 JOURNAL OF COSMETIC SCIENCE Although precipitation is the main method to isolate the complexes, this phenomenon has never been described in [3CD-containing emulsions or linked to the possible method of stabilization. Therefore, we plan to further examine this problem in the near future this could help to widen the uses of [3CD in industrial applications. REFERENCES (1) P.J. Sicard and M. H. Saniez, "Biosynthesis of Cycloglycosyltransferase and Obtention of Its Enzy- matic Reaction Products," in Cyc/odextrim a,d Their I,d•striM Uses', D. DuchSne, Ed. (Editions de Sant6, Paris, 1987), pp. 75-103. (2) Sunstar KK, JP Pate,t 09038253, 25 August 1990. (3) Kanegaoeuchi Chemical Industry Co, JP Pate, t 63248433, 14 October 1988. (4) Takeda Chemical Industries,JP Pate,t 88041541, 17 August 1988. (5) Kanebo KK, JP Pate,t 55092702, 14 July 1980. (6) Kobayashi Kosei KK, JP Pate, t 87031681, 9 July 1987. (7) K. Shimada, Y. Ohe, T. Ohguni, K. Kawano, J. Ishii, and T. Nakamura, Nippo, Shok•hi, Kogyo G•kk•ishi, 38, 16-20 (1991). (8) K. Shimada, K. Fujikawa, K. Yahara, and T. Nakamura, J. Agric. Food Chem, 40, 945-948 (1992). (9) J. Sjetli, Cyc/odextri, Tech,o/ogy (Kluwer Academic Publishers, Dordrecht, Germany, 1988), pp. 1-185, 307-334. (10) K. Shimada, K. Kawano, J. Ishii, and T. Nakamura, J. FoodSci., 57, 655-656 (1992). (11) Sansho Seiyaku KK, JP Pate,t 63208510, 30 August 1988. (12) D. DuchSne, F. Glomot, and C. Vautrin, "Pharmaceutical Applications of Cyclodextrins," in Cyc/o- dextrins' and Their Industrial Uses, D. Duch•ne, Ed. (Editions de Sant•, Paris, 1987), pp. 75-103. (13) R.J. Bergeron, D. M. Pillor, G. Gibeily, and W. P. Roberts, Bioorg. Chem., 7, 263-271 (1978). (14) S. Laurent, M. G. Ivanova, D. Pioch, J. Graille, and R. Verger, Chem. Phys'. Lipids, 70, 35-42 (1994).

d. Cosmet. sci., 50, 23-47 (January/February 1999) Human hair cuticle' Biologically conspired to the owner's advantage j. A. SWIFT, Department of Textiles and Fashion, De Montfort University, The Gateway, Leicester, LE1 9BH, England. Accepted for publication December 15, 1998. Synopsis The structure, chemistry, and physical properties of the human hair cuticle are reviewed, and the role of the covalently linked fatty acids, notably 18-methyl eicosanoic acid (18-MEA), contained therein, is discussed. Differential friction in hair is considered, and it is argued that this property normally facilitates the parallel alignment of hairs on the scalp and aids the rejection of macroscopic scalp surface detritus, to the owner's benefit. The hair seems to possess a natural process of surface repair that, by the gradual mechanical attrition of cuticle, aids in the retention of the hair's differential frictional behavior and in the retention of the associated benefits. INTRODUCTION 18-MEA in mammalian keratin fibers has recently been the subject of an excellent review by Dr Les Jones and the late Dr Don Rivett (1). This is taken with other relevant information (notably hair frictional behavior) in reaching the conclusion that 18-MEA is naturally and uniquely conspired to the well-being of the owner's hair. The structure, chemistry, and physical behavior of all mammalian keratin fibers and their cuticular layers are similar [with the exception of animals bearing quills (2)]. In this respect, it was thought not unreasonable for some of the information presented here to be culled from research on other animal fibers (notably sheep's wool) as being of direct relevance to the present considerations of human hair. The overall conclusions are as applicable to these other fibers as they are to human hair. GROSS STRUCTURE OF THE HAIR CUTICLE The central core, or cortex, of human head hair is covered by thin cellular sheets of cuticle that overlap each other from root to tip along the fiber (cf. Figure 1). Each sheet is approximately 0.5 pm thick and roughly 60 pm square, with rounded corners. They are wrapped circumferentially, either abutting each other or with some overlap, pre- senting the appearance in transverse section of a series of continuous layers. In a Iongi- 23