784 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS To rehydrate the medium, suspend 58 g of Bacto-Brilliant Green Agar in 1000 ml cold distilled water and heat to boiling to dissolve the medium completely. Distribute in tubes or bottles and sterilize in the autoclave for 15 min at 121 ø. A longer period of sterilization will tend to decrease the selectivity of the medium. The final reaction of the medium will be pH t3.9. Commercial form: Bacto-Brilliant Green Agar 0285-02 [Baird and Tatlock (London) Ltd.•. 1.16 Thioglycolate Broth (Modified Brewer) Peptone 15 g Yeast extract 5 g Sodium chloride 5 g Agar 1 g Thioglycolic acid 1 g Water 1 000 ml Dissolve the solids in the water with the aid of gentle heat. Add the thioglycolic acid and adjust to pH 8.5 with N/1 sodium hydroxide solution. Sterilize at 115 ø for 10 min. To prevent darkening of the medium, screw- caps should be loosened during autoclaving. Glucose 5 g Methylene blue, 1% aq. soln. 0.2 ml Adjust to pH 7.2. Add the glucose and dye solution. Mix well and sterilize at 115 ø for 10 min. This medium should be stored in screw-capped containers in the dark at 4 ø. If more than 20% of the medium shows a green colour before use, it should be heated in a boiling water bath or steamed for 5-10 min, and allowed to cool undisturbed. This treatment must not be repeated. Commercial form: Oxoid Granules CM23 or Tablets CM24. 1.17 Cetrimide Agar Proteose peptone no. 3 (Difco) 20 g New Zealand agar 15 g Glycerol 10 g Water to 1 000 ml Adjust this basal medium to pH 7.2 and sterilize at 121 ø for 15 min. To

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