61 
1)0 sufficient to consider only these two. The following is a brief ac- 
count of your agent's experience with, and methods of preparing, these 
two media: 
BEEF BROTH, 
The formula is the one most frequently used by Dr. S. A. Forbes and 
Prof. T. J. Burrill, of Champaign, 111.: One pound of round steak, free 
of fat. is chopped fine, placed in 1 quart of water, soft preferably, 
and allowed to stand over night. The next morning the meat is pressed 
dry. It is well to pour some of the liquid back on the meat, stir up 
thoroughly, let stand for half an hour, and press again. Strain the 
liquid through cheese-cloth, measure, and add enough to make the 
original quantity (1 quart). Pour into a liask. boil in steam, sterilize 
for an hour and a half. Strain through cheese-cloth or white flannel, 
niter, and allow to cool. Measure, and if necessary add enough dis- 
tilled water to make 1 quart. When about 60° C, neutralize with 
sodium carbonate (or if alkaline, with lactic acid). Cool to about 45° 
(_'.. and allow to stand for half an hour. Filter. Boil for au hour, cool 
to 60°, and filter through double thickness of best German filter paper. 
Sterilize for an hour, and let stand over night. If sediment forms, filter 
while cold. It is now safe to fill test tubes and proceed with three dis- 
continued sterilizations on as many successive days. In test tubes the 
sterilizations need not be continued for more thau twenty minutes. In 
large quantities an hour or more is required. 
The addition of the neutralizing agent often makes the liquid turbid. 
Added a little at a time and the liquid shaken, this cloudiness disap- 
pears. If so, it only indicates that the liquid is not yet neutral, ks 
the point of neutrality is reached the cloudiness disappears less per- 
fectly upon being shaken, and finally not at all, gradually forming a 
light, floeculent precipitate. The task of obtaining and retaining an 
absolute neutrality is a difficult one and the reaction just described, if 
carefully noted, will be of great assistance in making a delicate test. 
Some recommend the use of the white of an egg to assist in clarifying 
the broth. The method already detailed was so satisfactory that egg was 
used in only a few instances and then more as an experiment. It was 
found, if the broth was neutral or alkaline when the white was added, 
that it coagulated imperfectly when boiled and caused considerable 
difficulty. The broth had to be acidulated and then boiled to produce 
the proper coagulation. The filtrate was dear at first, but the process 
of neutralizing produced the same effect as to cloudiness and tine sedi- 
ment as already explained. 
The white of old eggs is somewhat more liquefied than that of fresh 
ones, and when used in a quantity of slightly acid broth it was difficult 
upon boiling to produce perfect coagulation. This merely emphasized 
the fact that only fresh eggs should be used in the work. 
