CHEMISTRY OF HUMAN HAIR CUTICLE 21 found (1) that virtually all the cystine in the cuticle is contained in the exocuticle-, A- and inner-layers. Measurements of electron micrographs of sectioned cuticle showed that these components occupy about 65•o of the total area of the cuticle. The average Concentration of « cystine in these 100 components may therefore be expected to be of the order of 200 x - 65 310 mol/1000 tool of amino acid. Such proteins containing nearly 1 in 3 amino acid residues as « cystine are likely to be extremely tough. From the present observations the compositions of the various sub- layers of the cuticle will prove of further interest. The present method for isolation of the cuticle should be of considerable value as a preliminary to the fractionation and analysis of these sub-layers. ACKNOWLEDGMENTS We are indebted to Dr J. C. Fletcher of the Wool Industries Research Association for the amino acid analyses of our materials and to our colleague Dr A. C. Brown for his work on freeze-dried fibres. (Received: 15th March 1973) REFERENCES (1) Swift, J. A. The electron histochemistry of cystine-containing proteins in thin transverse sections of human hair. J. Roy. Microsc. $oc. 88 449 (1968). (2) Swift, J. A. and Holmes, A. W. Degradation of human hair by papain. Part 3. Some electron microscope observations. Text. Res. J. 35 1014 (1965). (3) Kulkarni, V. G., Robson, R. M. and Robson, A. Studies on the orthocortex and para- cortex of merino wool. Appl. Polyrn. Syrnp. 18 127 (1971). (4) Parisot, A. and Derminot, J. The amino acid composition of various morphological frac- tions of wool isolated during progressive acid hydrolysis. Appl. Polym. Syrnp. 18 45 (1971). (5) Bradbury, J. H. and Leeder, J. D. Keratin fibres. IV. Structure of cuticle. Australian J. Biol. Sci. 23 843 (1970). (6) Lundgren, H. P. Separation of cortical cells of two types from disintegrated wool by means of density gradient columns. Proc. Int. Wool Textile Res. Conf., Australia, F, 200 (1955). (7) Wolfram, L. J. and Lindemann, M. K. O. Some observations on the hair cuticle. J. $oc. Cosmet. Chern. 22 839 (1971). (8) Swift, J. A. and Brown, A. C. The critical determination of fine changes in the surface architecture of human hair due to cosmetic treatment. J. $oc. Cos•net. Chem. 23 695 (1972). (9) Spurr, A. R. A low-viscosity epoxy resin embedding medium for electron microscopy. J. Ultrastruct. Res. 26 31 (1969).

22 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS (10) Bradbury, J. H. and Chapman, G. V. The chemical composition of wool. I. The separation and microscopic characterization of components produced by ultrasonic disintegration. Aust. J. Biol. Sci. 17 960 (1964). (11) Robbins, C. R. and Kelly, C. H. Amino acid composition of human hair. Text. Res. J. 40 891 (1970).