CULTURE METHODS 27 



Exercise 45. Preparation of Glycerin Bouillon 



Add 6 or 8 per cent glycerin to beef bouillon after nitration. 

 This medium is especially used for the cultivation of J3. tubercu- 

 losis, but may be used for other organisms with good results. A 

 solid medium is usually prepared by the addition of agar. 



Exercise 46. Preparation of van Delden's Solution for Cultivation 

 of Sulphate-Reducing Bacteria 



Dipotassium phosphate 0.5 g. 



Sodium lactate 5.0 g. 



Magnesium sulphate 1-Og. 



Asparagine 1-Og. 



Ferrous sulphate trace 



Tap water 1000.0 cc. 



Exercise 47. Preparation of Potato Gelatin (Eisner) 



1. (irate finely about 1 kg. of clean peeled potatoes. Weigh 

 the grated potato and add 1 cc. of distilled water for every gram 

 of potato. Place the mixture in a 2-liter flask and let it stand 

 in the ice chest for twelve hours. 



2. Strain through cheesecloth; then filter through Swedish 

 filter paper into a graduated cylinder. 



3. Add 15 per cent gelatin to the potato decoction and heat 

 in the Arnold sterilizer for sixty minutes. 



4. Estimate the reaction and render the final reaction plus 25. 



5. Cool the medium to below 60 C. and .clarify with egg- 

 white. 



6. Add 1 per cent potassium iodide to the medium. 



7. Filter through papier Chardin. 



8. Tube and give triple sterilization in the Arnold sterilizer. 



Exercise 48. Preparation of Heyden-Nahrstoff Agar 



1. Place 10 g. Heydeii-Nahrstoff in a flask containing 300 cc. 

 distilled water. Stir the powder until a good suspension is ob- 

 tained and allow the flask to stand overnight. Place 20 g. agar 

 shreds in 500 cc. water and allow it to stand overnight. 



2. Heat the Nahrstoff suspension in the Arnold sterilizer for 

 one to two hours, and filter while hot through paper. Drain the 



