2 34 PA THOGENIC BA CTERIA.

Koch produce immunity to tuberculosis by the adminis-
tration of TR, that he thinks it proved beyond a doubt
that the observations are correct.

In making the TR preparation Koch advises the use
of a fresh, highly virulent culture not too old. It must
be perfectly dried in a vacuum exsiccator, and the tritu-
ration, in order to be thorough, should not be done upon
more than 100 mg. of the bacilli at a time. A satisfac-
tory separation of the TR from TO is said only to occur
when the perfectly clear TO takes up at least 50 per cent
of the solid substance, as otherwise the quantity of TO in
the final preparation is so great as to produce undesirable
reactions.

The fluid is best preserved by the addition of 20 per
cent, of glycerin, which does not injure and prevents
decomposition of the TR.

The finished fluid contains 10 mg. of solid constituents
to the c.cm., and before administration should be diluted
with physiological salt solution (not solutions of carbolic
acid). When administering the remedy to man the in-
jections are made with a hypodermic syringe into the
tissues of the back. The beginning dose is -g-J-Q- of a mg.,
rapidly increased to 20 mg., the injections being made
daily.

In speaking of the results of experiments upon guinea-
pigs, Koch says:

"I have, in general, got the impression in these ex-
periments that full immunization sets in two or three
weeks after the use of large doses. A cure in tubercu-
lous guinea-pigs, animals in which the disease runs, as
is well known, a very rapid course, may, therefore, take
place only when the treatment is introduced early—as
early as one or two weeks after the infection with tuber-
culosis.

"This rule avails also for tuberculous human beings,
whose treatment must not be begun too late. ... A
patient who has but a few months to live cannot ex-
pect any value from the use of the remedy, and it will