24 A MANUAL OP BACTEEIOLOGY 



3. Add to the whey 1 per cent peptone, 2 per cent dextrose, 

 and 1.5 per cent agar. Cook, filter, and sterilize in the Arnold 

 sterilizer. 



Exercise 33. Preparation of Sugar Bouillon 



This is ordinary beef bouillon to which dextrose, lactose, or 

 saccharose has been added. It is prepared by adding to the or- 

 dinary bouillon (Exercise 8) 1 per cent by weight of one of the 

 above sugars. If lactose or saccharose bouillon is prepared, the 

 original bouillon should be free from inosite. This can be 

 tested by inoculating a fermentation tube containing the plain 

 bouillon with a gas-producing organism like B. coli. If no gas 

 is formed, the bouillon is free from inosite. Triple sterilization 

 in the Arnold sterilizer is best for sugar bouillon, since the heat 

 of the autoclave sometimes darkens the sugar. 



Exercise 34. Preparation of Sugar Gelatin 



To the sugar bouillon, prepared as in Exercise 33, add 12 

 per cent gelatin. Cook, neutralize, and filter as in Exercise 9. 

 Adjust the acidity and sterilize in the Arnold sterilizer. 



Exercise 35. Preparation of Litmus-Lactose Gelatin or Agar 



To ordinary nutrient gelatin, prepared as in Exercise 9, add 

 1 per cent of lactose by weight and enough litmus solution to 

 give a good blue color (see Exercise 80 for the preparation of 

 the litmus solution). It is better to add 15 per cent gelatin 

 instead of the usual 12 per cent. Tube the medium as usual 

 and sterilize in the Arnold sterilizer. Litmus-lactose agar may 

 be prepared by using 2 per cent agar instead of the gelatin 

 in the above. 



Exercise 36. Preparation of Glucose-Formate Bouillon (Kitasato) 



Add to a liter of beef bouillon 20 g. glucose and 4 g. sodium 

 formate. After they have dissolved, give triple sterilization in 

 the Arnold sterilizer. Solid media may be prepared by the 

 addition of gelatin or agar. This medium is useful in testing 

 the fermentative power of organisms. 



