36 THE BACTERIOLOGICAL EXAMINATION OF MILK 



3. Glucose or lactose bouillon — 



To 500 c.c. of nutrient bouillon add 10 grammes (2 per cent.) 

 of anhydrous glucose or lactose before final filtration. 



4. Glucose formate bouillon — 



To 500 c.c. of nutrient bouillon add 10 grammes (2 per cent.) 

 of anhydrous glucose, and 2 grammes (-4 per cent.) of sodium 

 formate before final filtration. 



5. Phenol bouillon — 



Dissolve in nutrient bouillon, before final filtration, carbolic acid 

 crystals in the proportion of 5 grammes (-5 per cent.), i gramme 

 (•I per cent), or 5 decigrammes (-05 per cent) per litre, according 

 to strength desired. 



6. Dextrose-free bouillon — 



Inoculate alkaline bouillon with a pure culture of B. coli or 

 other organism known to ferment dextrose, and incubate for 

 forty-eight hours at 37° C. Place in the Koch steriliser at 100° C. 

 for twenty minutes, allow to stand for twelve hours in a cool 

 place, decant supernatant fluid, filter, tube, and sterilise in the 

 autoclave at 115° C. for fifteen minutes. To test freedom from 

 dextrose fill a fermentation tube {see p. J'j') with the medium at 

 the same time, and sterilise with the tubes ; re-inoculate this when 

 cool with a culture of B. coli. If no fresh gas formation is observed 

 after incubation at 37° C. for forty-eight hours, the bouillon ma}^ 

 be considered dextrose-free. 



7. PariettVs bouillon — 



To tubes containing 10 c.c. of sterile nutrient bouillon add, by 

 means of a sterile calibrated pipette, -i, -2, and -3 c.c. of Parietti's 

 solution prepared as follows : — Dissolve 5 grammes carbolic acid 

 crystals in lOO c.c. of distilled water, and add 4 c.c. of pure hydro- 

 chloric acid. 



8. MacConkey's liquid medium — 



An emulsion of 20 grammes of dry peptone (Chapoteaut or 

 Witte) is made in 200 c.c. of distilled water at 60° C, and 5 

 grammes of commercial sodium taurocholate and 5 grammes of 

 glucose are then added and dissolved by stirring. The emulsion 

 is placed in a flask with 8cK) c.c. of distilled water, and heated in 

 the Koch at 100° C. for twenty minutes. It is then filtered through 

 Swedish filter paper into a sterile flask, and sufficient litmus solu- 



