PREPARATION OF CULTURE MEDIA 



19 



The filtered liquid is collected in a smaller funnel 

 (Fig- S> 0- A wire basket should be supported so as to 

 be inclined to an angle of about 45°, so as to allow the 

 proper arrangement of the tubes. 



Remove the plug of a cuhure-tube and quickly pass 

 the latter up the full length of the pipette (Fig. 5, /) , which 

 should be no less than 3 inches long. Open the pinch- 

 cock, fill the tube one-third full, and then quickly with- 

 draw the tube so as to 

 leave no trace of the me- 

 dium on the upper part of 

 the tube, and replace the 

 cotton stopper. If this 

 precaution is neglected, 

 the cotton stopper will stick 

 to the glass, which will 

 cause a great deal of an- 

 noyance later on and ex- 

 pose the medium to the 

 danger of contamination. 

 Fill thirty tubes in this 

 manner. 



If an exact volume of 

 medium is required in a 

 test-tube, an apparatus 

 such as is shown in Fig. 

 II may be employed. 



Fig. II 



Filling Definite Amount of Medium 



into Culture-Tube 



EXERCISE n. PREPARATION OF GLUCOSE-AGAR 



Glucose-agar is especially used for the demonstration 

 of gas-forming organisms. In such cases the glucose is 

 decomposed, and gas appears in bubbles throughout the 

 medium. 



