CHAPTER III 



PREPARATION OF CULTURE MEDIA 

 Each student is required to make up the following 

 amounts of culture media: 



Name of Medium 



Plain agar 



Glucose-agar 



Gelatin 



Potato 



Broth 



Dunham's solution 



Litmus milk 



Amoimt 



Number of Tubes 



looo g. 



25° g- 



i°o g- 



300 c.c. 

 300 c.c. 

 300 c.c. 



3° 

 20 



25 



10 



25 



25 

 25 



160 



EXERCISE I. PREPARATION OF NUTRIENT AGAR-AGAR 



1. Weigh the saucepan without the lid accurately 

 and make note of the weight. 



2. Measure into the saucepan 1000 c.c. of tap-water, 

 adding about 300 c.c. of water to allow for evaporation, 

 and heat over gas. 



3. Cut and shred 15 g. of agar-agar (ij per cent.), 

 add to the water, and boil slowly, with constant stirring, 

 until perfectly dissolved, taking care not to overheat. 



4. Add 3 g. of extract of beef. When dissolved, 

 remove the saucepan from the flame, and 



5. Slowly dust 10 (i per cent.) g. of Witte's peptone 

 on the surface, constantly stirring until perfectly dissolved. 

 Avoid allowing the peptone to clump. 



Note. — Agar-agar (called simply "agar") is a watery ex- 

 tract of certain seaweeds found on the Pacific coast of Asia. 



