HYGIENIC MANUFACTURE AND PRESERVATION 781 Dissolve the peptone, sodium chloride and sodium taurocholate in the water by heating. Adjust to pH 8.0 and boil for 20 min. Cool, filter, and adjust to pH 7.4. Add the lactose and indicator solution, mix and distribute into tubes containing inverted Durham's tubes. Sterilize at 115 ø for 15 min. Commercial form: Oxoid Granules CMSa or Tablets CM{3a. 1.07 Plate Count Agar (Tryptone Glucose Yeast Extract Agar) Tryptone 5 g Yeast extract 2.5 g D-Glucose 1 g Agar 15 g Water to 1 000 ml Add the ingredients to the water and dissolve by steaming. Adjust to pH 7.0, dispense as required and sterilize at 121 ø for 15 min. Commercial form: Oxoid Granules CM325 or Tablets CM32(3. 1.08 Robertson's Cooked Meat Medium Minced meat 1 000 g 0.05 N Sodium hydroxide soln. 1 000 ml Add the minced meat to the sodium hydroxide solution. Mix well and heat to boiling. Simmer for 20 min with frequent stirring. Skim off the fat and check pH which should be about 7.5. Strain through gauze or muslin, squeeze out excess liquor, and dry the meat particles at a temperature below 50 ø. For use, place sufficient dried meat in a screw-capped container to a depth of about 2.5 cm and add sufficient Nutrient Broth to give a depth of above 5.0 cm. Sterilize at 115 ø for 20 min. Avoid rapid release of pressure in the autoclave after sterilization. Although called Robertson's Cooked Meat Medium, the method of preparation differs considerably from the original. Commercial form: Oxoid Granules CM81 or Tablets CM82. 1.09 Sabmt, raud Dextrose Agar Mycological Peptone (Oxoid L40) 10 g Dextrose 40 g Agar 15 g Water to 1 000 ml Dissolve in a steamer and adjust pH to 5.0. Sterilize by autoclaving at 115 ø for 10 min. Commercial form: Oxoid Granules CM41 or Tablets CM42.

782 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS 1.10 Sabouraud Liquid Medium Pancreatic digest of casein (Oxoid L42) 5 g Peptic digest of fresh meat (Oxoid L49) 5 g Dextrose 20 g Water to 1 000 ml Dissolve in a steamer and adjust pH to 5.7. Autoclave at 115 ø for 15 min. Commercial form: Oxoid Granules CM 147 or Tablets CM 148. 1.11 Malt Extract Agar Malt extract 30 g Mycological Peptone 5 g Agar 15 g Water to 1 000 ml (p}• 5.4) Add all the ingredients to the distilled water and heat in a steamer until dissolved. Distribute as required and sterilize at 121 ø for 15 min. In order to inhibit the growth of bacteria, the medium may be acidified to pH 3.5. This is done by adding a sterile 10% lactic acid solution (or a sterile 10% citric acid solution) to the liquefied medium immediately before pouring the plates. The exact amount of acid to be added to adjust the medium to pH 3.5 will depend upon the make or batch of constituents used. Commercial form: Oxoid Granules CM59 or Tablets CM60. 1.12 Malt Extract Broth Malt extract (Oxoid L39) 17 g Mycological Peptone (Oxoid L40) 3 g Water to 1 000 ml (pH 5.4 approx.) Prepare medium according to the manufacturer's directions. Commercial form: Oxoid Granules CM57 or Tablets CM58. 1.13 Salt Meat Broth Peptone (Oxoid L$7) Lab-Lemco beef extract Neutral ox-heart tissue 10 g 10 g 3O g