GENERAL BACTERIOLOGY 
103 
order that the medium, when coagulated, will form a 
slant in the tube (Fig. 16). 
Actual Preparation of Various Culture Media 
1. Meat Extract Agar 
Agar is a Japanese seaweed. 
Meat extract agar is the most commonly used medium. 
Staphylococci typhoid and colon bacilli grow well on 
this. Other bacteria require richer media. 
(a) Pour into an agate vessel 1,000 c.c. of distilled 
water, add 15 grams of shredded (not powdered) agar, 
10 grams of Witte’s peptone, 5 grams of sodium chloride 
and 5 grams of Liebig’s meat extract. 
(b) Heat until agar is completely dissolved (thirty to 
forty-five minutes). 
(c) Add enough water to make up for loss by evapora¬ 
tion. 
(d) Cool to 60° C. and add whites of two eggs. 
(e) Heat in Arnold’s sterilizer for thirty minutes, 
stir and heat fifteen minutes. 
(f) Add water to make up for loss by evaporation. 
Filter through cotton. 
(g) Titrate to the desired reaction (usually about 0.2 
per cent acid, to phenolphthalein). 
(h) Tube and sterilize in autoclave for thirty minutes 
at 15 pounds pressure. Slant. 
2. Meat Infusion Agar 
Meat infusion agar is one of the richer media, suitable 
for culturing streptococci, etc. 
(a) In a two-liter Erlenmeyer flask pour 1,000 c.c. of 
