HYGIENIC MANUFACTURE AND PRESERVATION 785 each 100 ml of the liquefied base add aseptically the following solutions, each made up in distilled water and then Seitz-filtered: Dipotassium hydrogen phosphate (K2HP04) 15% soln. 1.0 ml Magnesium sulphate (MgSO4.7H20) 15% soln. 1.0 ml Cetrimide B.P. 2% soln. 1.5 ml Mix well by inversion several times and pour into Petri dishes. Commercial form: Pseudosel Agar, Cat. No. 11553 (Becton, Dickinson U.K. Ltd.). 1.18 Peptone Water Diluent Neutralized bacteriological peptone (Oxoid L&I) 1 g Water to 1 000 ml (pH 7.0 approx.) Distribute as required and sterilize at 115 ø for 15 min. 1.19 Reinforced Clostridial Medium Yeast extract (Oxoid LoeO) Lab-Lemco beef extract 10.0 g Peptone (Oxoid L$7) 10.0 g Soluble starch 1.0 g Dextrose 5.0 g Cysteine hydrochloride 0.5 g Sodium chloride 5.0 g Sodium acetate 3.0 g Agar 0.5 g Water to 1 000 ml (pH 6.8 approx.) Prepare according to directions given for Oxoid materials. Commercial form: Oxoid Granules CM149 or Tablets CM150. 1.20 Reinforced Clostridial Agar Yeast extract (Oxoid LoeO) 3.0 g Lab-Lemco beef extract 10.0 g Peptone (Oxoid L$7) 10.0 g Dextrose 5.0 g Soluble starch 1.0 g Sodium chloride 5.0 g

78{3 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Sodium acetate 3.0 g Cysteine hydrochloride 0.5 g Agar 15.0 g Water to 1 000 ml (pH 6.8 approx.) Prepare according to directions given for Oxoid materials. Commercial form: Oxoid Granules CM151 or Tablets CM152. GENERAL REFERENCES Cowan, S. T. and Steel, K. J. Manual for the identification of medical bacteria (Appendix A) (1966) (Cambridge University Press, London). Harrigan, W. F. and McCance, M. E. Laboratory methods in microbiology (Appendix 2) (1966) (Academic Press, London). Cruickshank, R. Medical microbiology 1 lth edn. 760 (1965) (E. & S. Livingstone Ltd., London). The Oxoid Manual $rd edn. (1965) (Oxoid Ltd., London). Alwen, J. and Smith, D. G. J. Appl. Bacteriol. 801t89 (1967). Brown, V. I. and Lowbury, E. J. L. J. Clin. Pathol. 18 752 (1965).