478 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS cII CI2 O= Protein/polysaccharide matrix • =Lipid molecule Figure 4. Schematic diagram of corneum intercellular junction. CI, cell interior CM, cell membrane H, hygroscopic molecule. the junction is necessary to account for failure of the NMF to be removed by aqueous extraction while the small salt ions used here can enter the structure. It is envisaged that the initial entry of small ions into the central region of the intercellular junction occurs at the surface of the corneum where desquamation results in a breakdown of the lipid bilayer. After entry has been gained, these small ions can diffuse through the entire intercellular system which is continuous throughout the corneum. The above model is somewhat speculative and additional work is re- quired to establish its validity. For example, no effect should be observed on native corneum due to ions above a critical size but these should still reduce the modulus of solvent extracted corneum. The effect of the same ionic species at different water activities and of different salts at the same water activity (specific ion effect) should afford additional information re- garding the mechanism of action of such species on the corneum structure. (Received: loth March 1972) REFERENCES (1) Park A. C. and Baddiel, C. B. Rheology of stratum corneum I. A molecular interpretation of the stress-strain curve. J. Soc. Cosmet. Chem. 23 26 (1972). (2) Park, A. C. and Baddid, C. B. Rheology of stratum corneum II. A physico-chemical investigation of factors influencing the water content of the corneum. J. Soc. Cosmet. Chem. 23 36 (1972).

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