MECHANICAL PROPERTIES OF SKIN 343 350 300 250 E o 200 E 150 100 E'--31 D + 82.5 r=.984 E'--23 D + 78.5 r=.986 50 I I I I 0 2 4 6 8 Diameter (ram) Figure 6. Effect of tape diameter (D) on the elastic modulus of skin (lower leg). Data are for two different subjects.

344 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Table II Variation in E' with Vertical Position Along the Lower Leg, Outer Aspect of the Calf (Mean Values for Five Panelists Selected for Dry Skin) Distance below Glycerol-treated Sites Water-treated Sites knee joint Initial Final Initial Final 10 cm 207 -- 71 142 + 49 149 --- 55 178 + 72 15 cm 353 ----- 119 252 ----- 55 304 _+ 99 319 --- 93 20cm 451 --- 46 313 -- 94 415 -- 166 448 + 184 amplitude and driving frequency in a complex manner, and the analysis procedure derived above is no longer valid. A theory describing the nonlinear behavior of stratum corneum under uniaxial tension in vitro has been presented recently (26). This approach would not be tractable for dynamic viscoelastic measurements such as ours. Rather, it is appropriate to apply harmonic analysis to the displacement and to apply equations 700 600 -- 500 3OO 2OO IO0 I I I I I • I 1 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 SKIN GRADE -" Better Skin Figure 7. Elastic modulus of skin (lower leg) vs. skin grade.