GENERAL BACTERIOLOGY 
105 
4. Meat Infusion Broth 
Meat infusion broth corresponds to meat infusion agar. 
It is prepared exactly as the meat infusion agar 
(Medium No. 2) except that the agar is omitted, and 
sterilized like it (in Arnold’s sterilizer for thirty min¬ 
utes on three successive days). 
5. Sugar-free Broth 
Sugar-free broth is used for making different sugar 
media. Prepare the broth just as the meat extract broth 
(No. 3) is prepared. 
After the step b, add 10 c. c. of a twenty-four-hour-old 
culture of colon bacillus. Then incubate at 37° C. for 
twenty-four hours. (The colon bacillus will destroy all 
sugar present.) Heat for thirty minutes in autoclave at 
15 pounds pressure. Add water up to 1,000 c.c., filter 
through paper and titrate. 
6. Sugar Broths 
After No. 5 has been prepared (the sugar-free broth) 
add different sugars (dextrose, lactose, saccharose, etc.), 
in proportion of 1 per cent tube in fermentation tubes, 
and heat for twenty minutes (not more, as it will spoil 
the sugars) in Arnold’s sterilizer on three successive days. 
(Instead of fermentation tubes one can use the following: 
tube in ordinary test tubes; when tubed, place into eacli 
test tube a very small tube (2x 1 / 4 inch) inverting it, so 
that its mouth rests against the bottom of the larger 
tube. During the sterilization the medium will be forced 
up into the smaller tube, and if fermentation will take 
place upon inoculation, the empty space where gas is 
collected in the small tube will show it. 
