NUTRIENT AGAR-AGAR. gl 



what tedious and time-taking experience. This is owing 

 mainly to lack of patience and failure to adhere strictly 

 to the rules laid down for the preparation of this medium. 

 Many methods are recommended for its preparation ; 

 almost every worker has some slight modification of his 

 own. 



The methods that have given us the best results, 

 and from which there are no grounds for deviating, are 

 as follows : 



Prepare the bouillon in the usual way. Agar-agar 

 reacts neutral, so that the bouillon may be neutralized 

 before the agar is added. Then add finely-chopped agar 

 in the proportion of 1 to 1.5 per cent. Place the mix- 

 ture in a porcelain-lined iron vessel and make a mark 

 on the sides of the vessel at which the level of the fluid 

 stands, add about 250 c.c. to 300 c.c. of water and allow 

 the mass to boil slowly, occasionally stirring, over a free 

 flame, for from one and one-half to two hours. Care 

 must be taken that it does not boil over the sides of the 

 vessel. From time to time observe if the fluid has 

 fallen below the mark of its original level; if it has, 

 add water until its original volume is restored. At the 

 end of the time given remove the flame and place the 

 vessel containing the mixture in a large dish of cold 

 water ; stir the agar continuously until it has cooled down 

 to about 68°-70° C, and then add the whites of two 

 eggs which have been beaten up in about 50 c.c. of 

 water; or the ordinary dried albumin of commerce 

 may be dissolved in cold water in the proportion of 

 about 10 per cent., and used. The results are equally 

 as good as where eggs are used. Mix this carefully 

 throughout the agar, and allow the mass to boil slowly 

 for about another half-hour, observing all the while the 



