374 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS the least polar glucosylceramide has suggested a specific role in assembly of the lameliar granules in the epidermal granular cells. Epidermal tissues of birds and reptiles have also been found to contain lameliar granules and ceramides, gluco- sylceramides, and gangliosides. However, in these animals, unlike mammals, much of the polar lipid remains within the cells when they keratinize and the glucosylceramides are not lost from the keratinized tissues. Nevertheless, it is the polar lipids which appear to constitute the barrier to water loss in all of the terrestrial vertebrates the nonpolar lipids, such as those produced by the sebaceous glands in mammals, the preen glands in birds, and the epidermis in reptiles, do not contribute significantly to the water barrier. Sebum: composition and secretion rate Derek R. Highley, Ph.D., Mary Kay Cosmetics, Inc., 1330 Regal Row, Dallas, TX 75247. Methodology for the accurate and reproducible determination of sebum composition and secretion rate is of considerable interest. This is because of the role of sebum in the etiology of ache and the number of cosmetic products that are designed to overcome its negative effects on the appearance of skin and hair. Implicit in the validity of methods used to measure sebum secretion rate is the assumption that the rate of secretion is independent of the amount of sebum or surface lipid present on the skin surface. The gravimetric and photometric techniques are most frequently employed to mea- sure this phenomenon. Both have advantages and drawbacks. Thin layer chromatography is used for qualitative and quantitative analysis of sebum and surface lipid composition. Infrared spectroscopy is also used as a qualitative measure. The techniques related to the measurement of sebum secretion rate and to the analysis of sebum and surface lipid are discussed in detail. Advantages, shortcomings and precautions required are emphasized. Some factors affecting the perception of hair oiliness James L. Solan, Gillette Research Institute, 1413 Research Blvd., Rockville, MD 20850. The appearance of human hair changes with time after washing until a point is reached where it is perceived to be oily. This is a consumer-perceived attribute and represents the interaction of a number of objective physical hair properties, rather than a unique measurable property. Some of the important factors include the amount, type, and excretion rate of lipid material, lipid properties, sweat compo- nents, endogenous and exogenous particulate deposits and hair geometry, density and spacing. A discussion of all of these factors being beyond the scope of this paper, attention is focused on certain of these hair properties, and experimental tech- niques for hair condition assessment as well as for collection and evaluation of hair soil are described. Statistical techniques employed to determine the interaction of the many factors involved in the oily condition and the identification of the dominant parameters are described. In addition, the results of initial attempts to develop a mathematical relation- ship between the relevant physical properties are presented.