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PRINCIPLES OF BACTERIOLOGY 
water and put 1 lb. of finely chopped lean beef, and put 
in the ice box over night. 
(b) Boil for twenty to thirty minutes, make up loss 
of water, and filter through a cotton gauze filter (2 or 3 
layers of gauze lined with cotton; when no more fluid 
runs through, gather the edges of the gauze over the cot¬ 
ton and squeeze it dry). 
(c) Add 10 grams of peptone and 5 grams of sodium 
chloride and heat (not over 50° C.) until peptone is 
dissolved. 
(d) Add 15 grams of shredded agar and boil until 
agar is dissolved. Make up to 1,000 c.c. 
(e) Heat for thirty minutes in Arnold’s sterilizer, stir, 
and reheat for fifteen minutes. 
(f) Titrate, adjust the reaction to 0.2 to 0.5 per cent 
acid, filter through cotton and tube. 
(g) Sterilize thirty minutes in Arnold’s sterilizer on 
three successive days. Slant. 
3. Meat Extract Broth 
Meat extract broth is a liquid medium corresponding 
to meat extract agar. 
(a) To 1,000 c.c. of water add 10 grams of peptone, 5 
grams of Liebig’s meat extract, and 5 grams of sodium 
chloride. 
(b) Heat until dissolved, and add water up to 1,000 
c.c. 
(c) Titrate and filter through paper (if not clear, add 
whites of two eggs, heat for thirty minutes in Arnold’s 
sterilizer, and then filter through cotton). 
(d) Tube and sterile in autoclave thirty minutes at 15 
pounds pressure. 
