PREPARATION OF NUTRIENT MEDIA. 65 



litre of distilled water. Place the vessel in an ice- 

 pail, ice-cupboard, or in winter in a cold cellar, 

 and leave for the night. Next morning commence 

 with the preparation of all requisite apparatus. 

 Thoroughly wash, rinse with alcohol, and allow to 

 dry, about 100 test-tubes. Plug the mouth of the 

 test-tubes with cotton wool, taking care that the 

 plugs fit firmly, but not too tightly. Place them 

 in their wire cages in the hot-air steriliser to be 

 heated for an hour at a temperature of 150 C. 

 In the same manner cleanse and sterilise several 

 flasks and a small glass funnel. In the meantime 

 the meat infusion must be again well shaken, 

 and the liquid portion separated by filtering and 

 squeezing through a linen cloth. The red juice 

 thus obtained must be brought up to a litre by 

 again transferring it to a large measuring glass 

 and adding distilled water. It is then poured into 

 a sufficiently large and strong beaker; and set aside 

 after the addition of 



10 grammes of peptonum siccum. 

 5 grammes of common salt. 

 100 grammes of best gelatine. 



In about half-an-hour the gelatine is sufficiently 

 softened, and subsequent gently heating in a water- 

 bath causes it to be completely dissolved. The 

 danger of breaking the beaker may be avoided by 

 placing a cloth several times folded at the bottom 

 of the water-bath. 



