26 CULTURE MEDIA 



bovine tuberculosis as plain glucose bouillon. Tim is better than the various 

 white of egg substitutes usually recommended. (Pouring a little alcohol in the mor- 

 tar 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 reintroducing 

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

 is essential for growing tubercle bacilli. Dorset's egg medium for the cultivation 

 of tubercle bacilli consists of the whole egg, which is emulsified as above, and heated 

 at 70 C. for from four to five hours each day for two days. To provide moisture 

 about i c.c. of sterile 6% glycerine solution is added to each slant. 



HYDROCELE, AND BLOOD AGAR. 



To tubes of melted agar at 50 C, add from i to 3 c.c. of hydrocele or ascitic 

 fluid, observing aseptic precautions. For blood agar the blood from a vein should 

 be received into a sodium citrate salt solution to prevent coagulation, and added 

 subsequently as for hydrocele fluid. Allow the agar to solidify as a slant, or as a 

 poured plate. 



BLOOD-STREAKED AGAR. 



Sterilize the lobe of the ear and puncture with a sterile needle. Collect the ex- 

 uding blood on a large platinum loop and smear it over the surface of an agar slant. 

 It is advisable to incubate over night as a test for sterility. Plates or slants of glycer- 

 ine agar of neutral reaction smeared with blood give the best results when such 

 delicate pathogens as pneumococci, streptococci, gonococci or meningococci are to 

 be cultured. 



BILE MEDIA. 



Secure ox bile from the abattoir or human bile from cases of gall-bladder drain- 

 age in hospitals. Put about 10 c.c. in each tube and sterilize. Some prefer to add 

 i% of peptone. Conradi's medium is ox bile containing 10% of glycerine and 2% 

 of peptone. This is the medium for blood cultures in typhoid, etc. 



The bile lactose medium now used in water analysis is made by adding i% of 

 lactose to ox bile and tubing in fermentation tubes. As a substitute for fresh bile 

 one may use a 15 to 20% solution of a good quality of inspissated ox gall (Fel Bovis 

 Purificatum). A liver bouillon made by using 500 grams of finely divided beef 

 liver in 1000 c.c. of water with i% peptone, and prepared as for meat infusion broth, 

 is a good substitute for bile. 



RECTOR'S BILE LACTOSE NEUTRAL RED MEDIUM. 



This is recommended in the isolation of the colon bacillus as superior to lactose 

 litmus agar. It consists of 10% of dried ox bile, i% of peptone, and i 1/2% agar. 



