26 A MANUAL OF BACTERIOLOGY 



Exercise 41. Preparation of MacConkey's Bile Salt Broth for Isolating 

 Intestinal Bacteria 



1. Place 20 g. Witte's peptone in 200 cc. distilled water 

 previously warmed to 60 C. Stir until the peptone is in 

 suspension. 



2. Weigh out 5 g. sodium taurocholate (commercial) and 5 g. 

 glucose and dissolve in the peptone water. 



3. Wash the peptone water into a flask with distilled water 

 and make the volume up to 1 liter. Cook the solution in the 

 steamer for twenty minutes at 100 C. Filter through paper 

 into a flask. 



4. Add either (a) sterile litmus solution sufficient to give the 

 medium a deep purple or (b) 5 cc. of a freshly prepared 1 per 

 cent solution of neutral red. 



5. Fill fermentation tubes, plug, and sterilize in the Arnold 

 sterilizer. 



Exercise 42. Preparation of Modified Giltay and Aberson's Fluid for 

 Denitrifying Organisms 



Distilled water 1000.00 cc. 



Potasshim nitrate . . . 2.00 g. 



Magnesium sulphate 2.00 g. 



Citric acid 5.00 g. 



Dipotassium phosphate 2.00 g. 



Calcium chloride 0.20 g. 



Anhydrous sodium carbonate 4.25 g. 



The solution should be neutralized by the addition of potas- 

 sium hydrate if, after boiling, it shows any acidity. 



Exercise 43. Preparation of Iron Bouillon for Detecting the Presence of 

 Hydrogen Sulphide 



Add 1 g. ferric tartrate (or lactate) to 1 liter beef bouillon. 

 Sterilize in Arnold sterilizer. 



Exercise 44. Preparation of Lead Bouillon for Detecting the Presence 

 of Hydrogen Sulphide 



Add 1 g. lead acetate to 1 liter beef bouillon. Sterilize in the 

 Arnold sterilizer. 



