GLYCERINE POTATO BOUILLON 203 



Lactose Litmus Bouillon (Lakmus Molke). 



1. Weight out peptone, 4 grammes, and emulsify it with 

 200 c.c. meat extract (vide page 148), previously heated to 60 C. 



2. Weigh out salt, 2 grammes, and lactose, 20 grammes, and mix 

 with the emulsion. 



3. Wash the mixture into a sterile litre flask with 200 c.c. 

 meat extract and add 600 c.c. distilled water. 



4. Heat in the steamer at 100 C. for thirty minutes, to com- 

 pletely dissolve the peptone, etc. 



5 . Neutralise carefully to litmus paper by the successive additions 

 of small quantities of decinormal soda solution. 



6. Replace in the steamer for twenty minutes to precipitate 

 phosphates, etc. 



7. Filter through two thicknesses of Swedish filter paper. 



8. Add sterile litmus solution, sufficient to colour the medium 

 a deep purple. 



9. Tube, and sterilise as for bouillon. 



Lactose Litmus Gelatine (Wurtz). 



1. Prepare nutrient gelatine (vide page 164, sections i to 4). 



2. Render the reaction of the medium mass 5. 



3. Replace in the steamer at 100 C. for twenty minutes. 



4. Clarify with egg as for gelatine. 



5. Weigh out lactose, 20 grammes ( = 2 per cent.), and dissolve 

 it in the medium. 



6. Filter through papier Chardin. 



7. Add sufficient sterile litmus solution to colour the medium 

 pale lavender. 



8. Tube, and sterilise as for nutrient gelatine. 



Lactose Litmus Agar (Wurtz). 



1. Prepare nutrient agar (vide page 167, sections i to 4). 



2. Render the reaction of the medium mass 5. 



3. Replace in the steamer at 100 C. for twenty minutes. 



4. Cool to 60 C. and clarify with egg as for nutrient agar. 



5. Weigh out lactose, 20 grammes ( = 2 per cent.), and dissolve 

 it in the medium. 



6. Filter through papier Chardin, using the hot-water funnel. 



7. Add sterile litmus solution, sufficient to colour the medium 

 a pale lavender. 



8. Tube, and sterilise as for nutrient agar. 



Glycerine Potato Bouillon. 



1. Take i kilo of potatoes, wash thoroughly in water, peel, 

 and grate finely on a bread-grater. 



2. Weigh the potato gratings, place them in a 2-litre flask, 



