426 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS (27) (28) (29) (30) (31) (32) (33) (34) (35) (36) (37) (38) (39) (40) (41) (42) (43) (44) (46) (47) (48) (49) (50) (51) (25) Shooter, R. A., Walker, K. A., Williams, V. R., Horgan, G. M., Parker, M. T., Asheshov, E. H. and Bullimore, J. F. Faecal carriage of Pseudomonas aeruginosa in hospital patients possible spread from patient to patient. Lancet ii 1331 (1966). (26) Shooter, R. A., Cooke, E. M., Gaya, H., Kumar, P., Patel, N., Parker, M. T., Thom, B. T. and France, D. R. Food and medicaments as possible sources of hospital strains of Pseudo- monas aeruginosa. Lancet i 1227 (1969). Hooper, W. L. The nature and extent of the microbial contamination of pharmaceutical preparations in hospital. Symposium on 'Microbial control', London (29 September 1971). Buck, A. C. and Cooke, E. M. The fate of ingested Pseudomonas aeruginosa in normal persons. J. Med. Microbiol. 2 521 (1969). Gaya, H., Adnitt, P. I. and Turner, P. Changes in the gut flora after cephalexin treatment. Brit. Med. J. 2 624 (1970). Wilson, G. S. and Miles, A. A. in Topley, W. W. C. and Wilson, G. S. Principles of Bac- teriology and Immunity, 5th edn, 1922 (1964) (Edward Arnold, London). Kuntz, L. J. and Ouchterlony, O. T. G. Salmonellosis originating in a hospital a newly recognized source of infection. New Engl. J. Med. 253 761 (1955). McCall, C. E., Collins, R. N., Jones, D. B., Kauffmann, A. F. and Brachman, P.S. An inter- state outbreak of salmonellosis traced to a contaminated food supplement. Am. J. Epidemiol. 84 32 (1966). Stoodley, B. J. and Thom, B. T. Observations on the intestinal carriage of Pseudomonas aeruginosa. J. Med. Microbiol. 3 367 (1970). Burkholder, W. H. Sour skin, a bacterial rot of onion bulbs. Phytopathology 40 115 (1950). Morris, M. B. and Roberts, J. B. A group of pseudomonads able to synthesize poly-13- hydroxybutyric acid. Nature (London) 193 1538 (1959). Philips, I., Eikyn, S., Curtis, M. A. and Snell, J. J. S. Pseudomonas cepacia (multivorans) septicaemia in an intensive care unit. Lancet i 375 (1971). Speller, D.C. E., Stephens, M. E. and Viant, A. C. Hospital infection with Pseudomonas cepacia. Lancet i 798 (1971). Baumann, P., Doudoroff, M. and Stanier, R. Y. A study of the moraxella group. II. Oxidase-negative species (genus Acinetobacter). J. Bacteriol. 95 1520 (1968). Taplin, D., Rebell, G. and Zias, N. The human skin as a source of Mima-Herellea infections. J. Am. Med. Assoc. 186 952 (1963). Adair, F. W., Geftic, S. G. and Gelzer, J. Resistance of Pseudornonas to quaternary ammo- nium compounds. I. Growth in benzalkonium chloride solution. Appl. Microbiol. 18 299 (1969). Lowbury, E. J. L. and Fox, J. The influence of atmospheric drying on the survival of wound flora. J. Hyg. Cambridge 51 203 (1953). Burdon, D. W. and Whitby, J. L. Contamination of hospital disinfectants with Pseudomonas species. Brit. Med. J. 2 153 (1967). Bassett, D. C. J. The effect of pH on the multiplication of a pseudomonad in chlorhexidine and cetrimide. J. Clin. Pathol. 24 706 (1971). U.S. Department of Health, Education and Welfare. Nosocomial bacteraemias associated with intravenous fluid therapy--U.S.A. Morbidity and Mortality Weekly Report. Special supplement to 20 (No. 9, 12 March) (1971). (45) U.S. Department of Health, Education and Welfare. Follow-up on septicaemias associated with contaminated Abbott intravenous fluids---U.S.A. MorbMity and Mortality Weekly Report, 20 91 (No. 10, 26 March) (1971). Morse, L. J. and Schonbeck, L. E. Hand lotions--a potential nosocomial hazard. New Engl. J. Meal. 278 376 (1968). Ayliffe, G. A. J., Barrowcliff, D. F. and Lowbury, E. J. L. Contamination of disinfectants. Brit. Med. J. I 505 (1969). Knights, H. T. and Harvey, J. Hand creams containing hexachlorophene and cross infection with Gram-negative bacteria. New Zealand Med. J. 63 653 (1964). Palmer, P. H. and McCracken, L. M. Contaminated antiseptic solutions. Lancet il 776 (1970). Simmons, N. A. and Gardner, D. A. Bacterial contamination of a phenolic disinfectant. Brit. Med. J. 2 668 (1969). Bassett, D.C. J. Causes and prevention of sepsis due to Gram-negative bacteria common- source outbreaks. Proc. Roy. Soc. Med. 64 980 (1971).

J. Soc. Cosmet. Chem. 23 427-445 (1972) ¸ 1972 Society of Cosmetic Chemists of Great Britain Structural aspects of keratin fibres N.H. LEON* Synopsis--Rapid progress has been made in keratin research since the availability of ELECTRON MICROSCOPY and modern biochemistry. This REVIEW presents a general description of the structure of MAMMALIAN KERATIN FIBRES with special reference to HUMAN HAIR. It is intended primarily for cosmetic chemists who desire a brief survey of the subject. INTRODUCTION Hair and wool, in their natural (unstretched) state, belong to a group of proteins called a-keratins. The designation 'alpha' was used by Astbury and Woods (1) to indicate that the crystalline portions of these proteins have a particular X-ray diffraction pattern in common with various other fibrous proteins. This pattern was later shown to be associated with the a-helical structure for proteins proposed by Pauling, Corey and Branson (2). Keratins are defined by Lundgren and Ward (3) as 'natural, cellular systems of fibrous proteins cross-linked by cystine sulphur. They have evolved primarily as a barrier to the environment, serving to protect the higher vertebrates--amphibians, reptiles, birds and mammals--from the stresses of life. Keratins occur as the principal constituents of the horny layer of the epidermis and of related appendages, such as horns, hooves, scales, hair and feathers, that are derived from the skin'.'• AMINO ACID COMPOSITION OF KERATIN FIBRES Like other proteins, keratin fibres are polypeptides composed of some 18 different types of a-I•-amino acid residues of the general formula * Unilever Research Laboratory, 455 London Road, Isleworth, Middlesex. •' For a discussion of a more precise definition, see (4). 427