20 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS the hair cortex. From the foregoing the material released into suspension after 2« h under the defined conditions of shaking on the elliptoid shaker is clearly to be regarded as virtually pure cuticle. Amino acid analyses of our 2« h cuticle fraction and that of samples of the original hair are shown in Table I. Included in this table for comparison are Wolfram and Lindemann's results (7) which have been recalculated in terms of moles of each component/1000 mol of total amino acid. For all the amino acids except proline there is exceedingly good agreement between the two sets of cuticle analyses. There is some variation between the two separate analyses for whole hair but this is probably accounted for by natural variations from one individual to another (11). The cuticle evidently con- tains significantly higher concentrations of serine, proline (in the case of Wolfram and Lindemann's results), glycine, alanine, valine, cystine and lysine and lower concentrations of aspartic acid, threonine, glutamic acid, leucine and arginine than the cortex. In terms of the cystine content it is interesting to note that from electron histochemical observations we have Table 1. Amino acid composition of human hair and human hair cuticle Content in mol/1000 mol total amino acids analysed Amino acid Present results Wolfram and Lindemann's results (7) Cuticle Hair Cuticle Hair Cysteic acid 8.8 3.4 6.2 4.1 Aspattic acid 30.9 57.7 31.4 51.6 Threonine 44.1 74.5 43.1 71.7 Serine 168.9 115.2 170.3 125.1 Glutamic acid 92.5 129.5 88.7 118.5 Proline 64.6 68.0 94.2 76.1 Glycine 97.4 61.1 87.5 56.5 Alanine 56.6 46.2 52.3 44.9 Valine 68.7 49.8 67.4 52.4 « Cystine 202.2 167.3 196.7 185.6 Methionine 4.8 2.1 4.1 1.7 Isoleucine 20.3 25.4 19.5 22.5 Leucine 46.2 64.9 42.3 59.1 Tyrosine 17.0 21.4 14.0 20.4 Phenylalanine 12.1 16.5 12.0 16.0 Lysine 33.1 24.9 34.6 25.4 Histidine 4.5 7.1 5.5 8.0 Arginine 27.4 65.1 30.2 60.3

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).