58 MEDIA AND THEIR PREPARATION 
Haricot Decoction. Maccrate 50 to 60 gms. of white haricot beans 
in a liter of water for several hours in the cold. Boil for one-half hour. 
Pour on a coarse sieve, collect the liquid, and add to it 1 per cent of 
salt, 2 per cent of sugar and a pinch of sodium bicarbonate. Boil 
and filter through paper. Tube and sterilize at 115° C. 
This medium is used by Maze to cultivate the bacteria in nodules 
of leguminous plants. 
Malt Extract (Besson). 1. Grind up 100 gms. malt and add 1000 
ems. of H20. 
2. Heat to 56° C. for one hour; the starch is converted into maltose 
by the diastase and a true beer wort obtained 
3. Boil, filter through Chardin paper. 
4. Tube, sterilize at 115° C. 
Urine (Besson). 1. Boil some recently passed urine. 
2. If the reaction is markedly alkaline after boiling, add a little 
tartaric acid solution, testing the reaction with litmus paper. ~ 
3. Filter, tube and sterilize at 155° C. The composition of urine 
is altered by this proceeding, the urea in solution being decomposed 
at boiling temperature. It is better to sterilize through a Chamber- 
land bougie. 
Capaldi’s Egg Medium. A few loopfuls of egg yolk are added to 
a tube of liquefied agar, previously cooled to 45 to 47° C. 
Dorset’s Egg Medium. Eges are broken into a flask and the 
yolks broken with a needle or glass rod. The flask is shaken until 
the yolks and whites are thoroughly mixed. Foam formation should be 
avoided. Distribute in culture tubes and sterilize in a Koch inspis- 
sator or autoclave in the same manner as blood serum. 
Egg-Meat Mixture (Rettger, 1906). A. One-half pound of lean 
chopped beef is stirred up in 250 c.c. of water, and after neutralizing 
the meat acids with sodium carbonate, the mixture is heated in an 
Arnold sterilizer for thirty minutes, with occasional stirring. It is then 
set away in a cold place for several hours after which the fatty scum 
is removed. 
B. The whites of three eggs are mixed with 250 c.c. of water, and 
after neutralizing, the albumen is coagulated, with occasional stirring, 
by heating in the Arnold sterilizer for thirty minutes. 
A and B are then mixed and introduced into a liter flask, along 
with 2.5 gms. (0.5 per cent) of powdered calcium carbonate. The flask 
is plugged with cotton and sterilized for thirty minutes, at 110 to 112° C. 
(autoclave), 
