BILE SALT BROTH 199 



3. Weigh out 



Silicic acid 3.4 grammes 



and dissolve in 



Distilled water 100 c.c. 



4. Pour the silicic acid solution into a large porcelain basin. 



5. Mix equal quantities of the solutions A and B; then add 

 successive small quantities of the mixed salts to the silicic acid 

 solution, stirring continuously with a glass rod, until a jelly of 

 sufficiently firm consistence has been formed. 



6. Spread a layer of this jelly over the bottom of each of several 

 large capsules or "plates." 



7. Sterilise in the steamer at 100 C. for thirty minutes on each 

 of three consecutive days. 



Media for the Study of Water Bacteria. 



Naehrstoff Agar (Hesse and Niedner) . (For enumeration of water 

 organisms.) 



1. Weigh out: agar, 12.5 grammes and emulsify in 250 c.c. 

 distilled water. 



2. Wash the agar emulsion into a tared 2 -litre flask with a 

 further 250 c.c. distilled water. 



3. Dissolve by bubbling live steam through the mixture. 



4. Emulsify Naehrstoff-Heyden (albumose) 7 . 5 grammes in 

 200 c.c. cold distilled water and add to melted agar. 



5. Adjust weight of medium mass to the calculated figure for one 

 litre (1020 grammes) by addition of distilled water at 100 C. 



6. Clarify with white of egg and filter. 



7. Tube in quantities of 10 c.c. and sterilise in the steamer at 

 100 C. for twenty minutes on each of three successive days. 



Bile Salt Broth Double Strength. 



1. Weigh out Witte's peptone, 40 grammes, and emulsify with 

 300 c.c. distilled water previously warmed to 60 C. 



2. Wash the peptone emulsion into a litre flask with 600 c.c. 

 distilled water. 



3. Weigh out sodium taurocholate, 10 grammes, and glucose, 

 10 grammes; dissolve in 100 c.c. distilled water and add to the 

 peptone emulsion in the flask. 



4. Heat in the steamer at 100 C. for twenty minutes. 



5. Filter through Swedish filter paper into a sterile flask. 



6. Add sterile neutral litmus solution sufficient to colour the 

 medium to a deep purple. 



7. Fill into small Erlenmeyer -flasks in quantities of 25 c.c. 



8. Sterilise as for nutrient bouillon. 



