288 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS necessary to consider extreme conditions, i.e. the product most likely to support bacterial growth. Our results indicate that for certain products a very small number of bacteria only is necessary to contaminate a large batch of product. (Received: 20th March 1974) REFERENCES (1) Wedderburn, D. L. Advan. Pharm. Sci. 1 195 (1964). (2) Savin, J. A. Pharm. J. ii 285 (1967). (3) Morse, L. J., Williams, H. P., Green, R. P. Jr, Eldridge, E. E. and Rotta, J. R. N. Engl. J. Med. 277 472 (1967). (4) Bruch, C. W. Amer. Perfum. Cosmet. 86 45 (1971). (5) Dunnigan, A. P. and Evans, J. R. T. G. A. Cosmet. J. 2 1 39 (1970). (6) Tennenbaum, S. J. Soc. Cosmet. Chem. 18 797 (1967). (7) Bryce, D. M. and Smart, R. J. Soc. Cosmet. Chem. 16 187 (1965). (8) Collins, V. G. Proc. Soc. Water Treat. Exam. 12 40 (1963). (9) Collins, V. G. J. Appl. Bacteriol. 27 143 (1964). (10) Honeywell, G. E., Rueher, F. M. and Staperr, E. M. Devs. Ind. Microbiol. 3 306 (1961) (11) Chambers, C. W. and Clarke, N. A. Advan. AppL Microbiol. 8 105 (1966). (12) Silvey, J. K. G. and Roach, A. W. J. Am. Water Works Assoc. 56 60 (1964). (13) Geldreich, E. E. and Clark, H. F. J. Milk Food Technol. 28 351 (1965). (14) Leifson, E. Int. Bull. Bacteriol. Nomenclature Taxonomy 12 133 (1962). (15) Thistlethwayte, D. K. B. Amer. Perfum. Cosmet. 81 29 (1966). (16) Sykes, G. and Smart, R. Arner. Perfum. Cosmet. 84 45 (1969). (17) Castell, C. H. and McDermott, L. A. Food Res. 7 244 (1942). (18) Schuster, G. and Modde, H. Seifen Ole Fette Wachse 94 709 (1968). (19) Garvie, E. I. J. Bacteriol. 69 393 (1954). (20) Poynter, S. F. B. and Mead, G. C. J. Appl. Bacteriol. 27 182 (1964). (21) Bowen, L. Amer. Perfum. Cosmet. 85 65 (1970). (22) Burman, N. P. Discussion to Proc. Soc. Water Treat. Exam. 12 40 (1963). (23) Eisman, P. C., Kull, F. C. and Mayer, R. L. J. Amer. Pharm. Ass. Sci. Ed. 38 88 (1948) (24) Stamm, J. M., Engelhard, W. E. and Parsons, J. E. AppL Microbiol. 18 376 (1969). (25) Cowan, S. T. and Steel, K. J. Manual for the Identification of Medical Bacteria (1965) (Cambridge University Press, London). (26) Reports on Public Health and Medical Subjects No. 71. The Bacteriological Examination of Water Supplies (1969) (H.S.M.O., London).

J. Soc. Cosmet. Chem. 26, 289-297 (1975) ¸ 1975 Society of Cosmetic Chemists of Great Britain Hair breakage: microscope as a the scanning electron diagnostic tool A. C. BROWN and J. A. SWIFT* Presented on 28th August 1974 in London, at the 1FSCC Vlllth International Congress on 'Cosmetics--Quality and Safety' organized by the Society of Cosmetic Chemists of Great Brita#t Synopsis Physical techniques for studying the mechanical properties of HUMAN HAIR have been well established for many years and since the introduction of the SCANNING ELEC- TRON MICROSCOPE (SEM) 8 years ago, there has been some attempt to correlate, retrospectively, the structural appearance of deformed fibres with data obtained during mechanical straining experiments. A logical development is to combine these two techniques so that both physical and structural data could be collected simultaneously, thereby enabling a more detailed and accurate assessment of the breakdown of structural components to be made. The SEM, because of its great depth of focus, wide range of magnification and large area for specimen manipulation, has been adapted for conducting dynamic experiments in situ. In addi- tion, the manner in which the visual information was processed made direct recording of the results onto VIDEOTAPE possible. A number of simple mechanical specimen stages have been constructed for use in examining the structural deformation of hair fibres under various conditions of mechanical stress. The incorporation of d.c. micromotors into the SEM allowed accurate control of sample movement during experiments and miniature strain gauges were used so that continuous recordings of the changes in strain could be made. The nature of the structural breakdown in human hair during COMBING has been investi- gated, together with the changes taking place as a result of natural weathering. INTRODUCTION As the fashion for long hair has grown more popular in recent years so interest in hair weathering has increased. An opinion poll conducted * Unilever Research, Isleworth Laboratory, Unilever Ltd, 455 London Road, Isleworth, Middlesex. 289