BACTERIOLOGICAL TECHNIC 31 



EXERCISE 8. PREPARATION OF BROTH FROM 

 FRESH MEAT 



The following method has some advantages over 

 the previous method and is specially adapted to the 

 preparation of diphtheria toxin: 



1. Clean one pound beef or veal of adhering fat, 

 etc., and grind in a meat chopper. 



2. Cover with one liter of water and digest over 

 night at room temperature. 



3. Heat to 60 C. and digest at this temperature for 

 two hours. 



4. Boil for 30 minutes. 



5. Press the liquid from the meat in a meat press 

 (Fig. 1 8). Mix the meat with 



some more water, press out 

 again, and bring the volume of 

 the two combined liquids to I 

 liter. 



6. Dissolve in this 20 grams 

 pepton and 5 grams sodium 

 chlorid. 



7. Adjust the reaction to 

 i . 2 per cent acid with phenol- 

 phthalein as indicator. 



8. Filter until perfectly clear 

 and sterilize in the autoclave. 



FIG. Tg 

 Meat Press 



EXERCISE 9. PREPARATION OF BLOOD SERUM 



i. Fresh ox blood, horse blood, or dog's blood, 

 collected in sterile containers, is set aside in an ice 

 chest until the serum has separated. 



