BLOOD AGAR 31 



HYDROCELE, SERUM, ASCITIC AND MILK AGAR 



To tubes of melted agar at 5oC., add from i to 3 c.c. of hydrocele or ascitic fluid, 

 observing aseptic precautions. Allow the agar to solidify as a slant, or as a poured 

 plate. 



For milk agar we add 2 or 3 c.c. of plain or litmus milk to a tube of melted agar. 

 This makes an excellent plating medium for B. bulgaricus. When poured into a 

 plate it is opaque but the colonies stand out well. 



For obtaining sterile serum we generally use the apparatus described under 

 Blood Agar and as a rule take the blood from vein of arm in man or vein of neck of 

 sheep used for Wassermann work. The sterile serum separates from the clot and 

 can be pipetted off with a sterile pipette and added to the melted 2 to 3% agar as 

 above. A method recommended by Fildes is to take blood at the slaughter house 

 in sterile vessels, allow to clot and remove serum. Five c.c. of ether is added to 

 each 100 c.c. in a glass-stoppered bottle of which the stopper is fixed in and the mix- 

 ture heated for one hour in a water-bath at 45C. after which it is placed in the 

 incubator at 37C. for several days, by which time the serum is sterile. Before using 

 the ether is driven off at 45C. This is better than the old method of sterilizing 

 with 2% chloroform. 



BLOOD AGAR 



For obtaining blood to make blood agar we use the apparatus described under 

 blood culturing and shown in Fig. 8. We take human blood from the arm vein, 

 sheep blood from the neck vein, or rabbit blood from the heart. In the Erlenmeyer 

 flask of 100 c.c. capacity is placed 5 c.c. of sterile 10% sodium citrate solution pro- 

 vided we want to take 50 c.c. of blood from sheep or man. The final mixture to 

 prevent coagulation should contain about i% sodium citrate. As a rule we only 

 take about 25 c.c. from man or rabbit so 2^ c.c. of 10% citrate would. suffice. The 

 perforated rubber stopper is removed and replaced with the sterile cotton plug of 

 the flask and the fluid mixture pipetted off and added to the melted agar. 



Mixture is facilitated by rotating the tube rapidly between the hands. The 

 medium may be slanted or poured into plates. As this medium is satisfactory 

 for the growth of haemoglobinophilic organisms-,' as well as for others, we use it as a 

 routine plating medium, the others being nutrient agar and Endo. 



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 drainage 

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



