30 CULTURE MEDIA 



BLOOD-SERUM 



The blood of cattle should be collected in large pans or pails at the abattoir. 

 This vessel of blood should then be kept in the cold-storage room and the next morn- 

 ing the more or less clear serum will have been squeezed out from the clot. Collect 

 this serum and keep in the ice chest for future use. If to be kept for a long time, it 

 is advisable to add about 2% of chloroform to the serum in tightly corked flasks. 

 This will not only keep the serum, but will eventually sterilize it. 



To make Loffler's serum, take i part of glucose bouillon and 3 parts of blood- 

 serum. Mix, tube, and coagulate the albumin in the inspissator or rice cooker, 

 giving the tubes a proper slant before heating. Sterilize the following day in tl 

 autoclave as previously directed (7 pounds) or in the Arnold on three successive da} 



A SUBSTITUTE FOR ORDINARY BLOOD-SERUM 



Add from 10 to 15 c.c. of i% glucose bouillon to the white and yolk of one egg, 

 make a smooth mixture in a mortar and tube. Inspissate and sterilize as for ordi- 

 nary serum slants. The morphology of the diphtheria bacilli and the luxuriance of 

 growth is similar to that of cultures on Loffler's serum. 



When this medium is to be used for culturing tubercle bacilli add about i c.c. 

 of glycerine bouillon to each tube before final sterilization in the autoclave. The 

 cotton plugs should be paraffined to prevent drying of the slants in the incubator. 

 This medium seems to answer as a substitute for Dorsett's egg medium. (While 

 glycerine bouillon favors growth of human tuberculosis, it is not so satisfactory fc 

 bovine tuberculosis as plain glucose bouillon.) This is better than the various whit( 

 of egg substitutes usually recommended. (Pouring a little alcohol in the mort< 

 and moistening the sides by tilting, then burning off the alcohol, in a measure 

 sterilizes the mortar. If the egg is cracked open with a sterile knife, a medium can 

 be prepared which will be sterile as the result of the two-hour inspissation in the rice 

 cooker.) By covering the tube with a rubber cap or preferably, by heating the 

 plugged end of the test-tube, quickly withdrawing the cotton plug and dipping the 

 part of the plug which enters the tube into hot melted paraffin, then quickly reintro- 

 ducing the plug, the contents of the tube will be prevented from drying out. This 

 procedure is essential for growing tubercle bacilli. 



Egg media are excellent for culturing anaerobes. One can add about 5 drops of 

 i% neutral red aqueous solution to each egg, inspissating as above. The reddish 

 color appears in colonies producing acid and is of value in anaerobic work to make 

 such colonies more distinct. 



DORSETT'S EGG MEDIUM 



This is prepared by breaking whole eggs into a sterile flask, mixing thoroughly then 

 adding 25 c.c. water to every 4 eggs, straining through a sterile cloth and tubing 10 

 c.c. quantities. These tubes are slanted in an inspissator and kept at 73C. for 

 four or five hours on two successive days. On the third day a temperature of 76C. is 

 applied. Before inoculating add 3 or 4 drops of sterile water to each tube. The 

 tuberculous material should be rubbed into the surface well and the plugs paraffined. 



