AGAR-AGAR 117 



AGAR-AGAR 



To make agar : 



(a) Take 20 grams of powdered or chopped agar. 



(b) Add to 500 c.c. of water, place in a can in autoclave and 

 heat to 1 2oC. Then cool. 



(c) Add this to 500 c.c. of bouillon of double strength, making 

 1,000 c.c. 



(d) Neutralize. 



(e) Cool to 6oC. 



(/) Add the egg to the mixture, stir. 



(g) Boil till egg is coagulated thoroughly. 



(h) Titrate and adjust to desired acidity as given under bouil- 

 lon, and while boiling hot, filter through absorbent cotton 

 wet with boiling water. 



(i) Run into tubes. Sterilize. Slope the tubes for twelve 

 hours and store in dark place. 



To make glycerine agar add 5 percent of glycerine to the agar 

 before neutralizing. To make agar for tubercle bacilli, veal 

 bouillon may be employed, and glycerine must be added. 



Litmus Milk 



Carefully skimmed milk, to which litmus tincture has been 

 added, is run into tubes and sterilized. This is a valuable culture 

 medium. It is also a reagent. 



Potato Tubes 



i. Wash some large potatoes and with a Ravenel potato cutter, 

 cut out semi-cylinders of potato. Immerse in running water over- 

 night, in order to prevent them from turning black. It is well 

 to wash these bits of potato with i- 10,000 bichloride of mercury 

 six hours and running water over night. Some laboratories soak 

 their slices in sodium carbonate solution. It is desirable to know 



