NUTRIENT MEDIA AND METHODS OF CULTIVATION. 



103 



may be transferred to the test-tube water-bath, and heated for an 

 hour a day for three successive days. 



If the gelatine shows any turbidity after these processes it must 



FIG. 32. METHOD OF MAKING A FOLDED FILTER. 



be poured back from the test-tubes into a flask, boiled up for ten 

 minutes, and filtered once more, and the processes of sterilisation just 

 described must be repeated. 



FIG. 33. STEAM STERILISED 



Nutrient Agar-agar. Agar-agar is a substance prepared 

 from seaweed which grows on the coasts of Japan and India, 

 and is supplied in long crinkled strips. It boils at 90 C., and 



