62 JOURNAL OF COSMETIC SCIENCE theme parks at specified dates from January through May of 2001 and estimating hair length relative to specific anatomical positions, we conclude that about 13% of the US adult population currently has hair shoulder-length or longer, about 2.4% have hair reaching to the bottom of the shoulder blades or longer, about 0.3% have hair waist- length or longer, and only about 0.017% have hair buttocks-length or longer. Hair appreciably longer than buttock-length was not observed in this population. REFERENCES (1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) C. R. Robbins, Chemical and Physical Behavior of Human Hair, 4th ed. (Springer-Verlag, New York, 2001), pp. 4-6. C. R. Robbins, Chemical and Physical Behavior of Human Hair, 4th ed. (Springer-Verlag, New York, 2001), pp. 9-24. J. M. Barman, I. Astore, and V. Pecoraro, The normal trichogram of the adult,J. Invest. Dermatol., 44, 233-236 (1965). R. J. Myers and J. B. Hamilton, Regeneration and rate of growth of hairs in man, Ann. N.Y. Acad. Sci, 53, 562-568 (1951). C. R. Robbins, Chemical and Physical Behavior of Human Hair, 4th ed. (Springer-Verlag, New York, 2001), p. 9. Guinness Book of World Records 1999 (Facts on File, New York, 2000), p. 49. Guinness Book of World Records 1996 (Facts on File, New York, 1995), p. 13. M. Courtois, G. Loussouarn, C. Hourseau, and J. F. Grollier, Ageing and hair cycles., Br. J. DermatoL, 132, 86-93 (1995). C. R. Robbins, Chemical and Physical Behavior of Human Hair, 4th ed. (Springer-Verlag, New York, 2001), p. 11. A. O'Conner, BT Target Audience Study--Final Report, Colgate-Palmolive Company, March 6, 1973. C. R. Robbins, Chemical and Physical Behavior of Human Hair, 4th ed. (Springer-Verlag, New York, 2001), p. 17.

j. Cosmet. sci., 54, 63-83 (January/February 2003) The role of cationic conditioning compounds in reinforcement of the cuticula SIGRID B. RUETSCH, Y. K. KAMATH, and H.-D. WEIGMANN, TRI/Princeton, P.O. Box 625, Princeton, NJ 08542. Accepted for publication April 3, 2002. INTRODUCTION Everyday grooming practices result in ablation of the cuticula. This ablation is directly associated with the ease of scale lifting that occurs during the imposition of stresses on individual hair fibers during grooming, especially when encountering a snag. During extension, the cuticle cells release the stress of extension by moving relative to one another. This relative movement is accommodated by the deformation and fracture of intracuticular (endocuticle) and intercuticular (CMC) structures in the cuticular sheath. At high strains, failure of these intra- and intercuticular domains occurs, causing lifting of the edge of the exposed cuticle cell (1). In the cosmetic industry, conditioners are believed to be beneficial in preventing or at least significantly reducing long-term grooming damage to the hair fiber. This has been confirmed by various test methods developed at TRI. Principal among these are methods involving prolonged combing and fiber fatigue experiments. In addition to reducing stresses by friction reduction, the efficacy of these compounds can be attributed to the reinforcement of the cuticular sheath by strengthening the endocuticle, improvements in intercuticular adhesion, and subsequent prevention of scale lifting and scale chipping. Therefore, the core of this work investigates the effects of model cationic conditioning compounds of different molecular weight on the reinforcement of the cuticula, that is, on improvement of cuticular cohesion and prevention of scale lifting during extension. We have, therefore, attempted to quantify the scale-lifting behavior that occurs during longitudinal extension of unaltered hair fibers and hair fibers that have been exposed to treatments with high- and low-molecular-weight conditioners. Our results clearly in- dicate that treatment of hair with cationic polymeric and monomeric quaternary am- monium compounds improved cuticular cohesion and improved resistance to scale lift- ing. Comparison of the effects and performance of the compounds will be made. Mi- crofiuorometry and scanning electron microscopy (SEM) have been used in this work. In an associated study, we demonstrate improved cuticular cohesion by cationic corn- 63