The evening times., 1899-04-27

.
caused to grow upon medium that has 2
slight acid reaction. When liquid cultures
of the tubercle bacilli have been once in
oculated and are growing well, Il is very
much easier to inoculate fresh culture me-
dia from liquid cultures rather than from
the jelly cultures. with which it is always
necessary to start.
The transference of a particule contain
ing large number of the germs from the
surface Of one flask to serve as seed upon
the surface Of another flask will give what
is commonly called new generation. AS
these transfers are usually made every
month or six weeks, 1t is possible, in the
course of q few years, to obtain a germ
which is direct descendant of the one
originally used, but removed from 1t by
| many generations. This continued trans
ference CT the bacteria from one nutrient
flask to another has the effect in many
cases Of changing some Of the properties
| Of the germ.
! I'm the laboratory Of the biochemic d.
vision it has been found. in connection
with the tubercle germ, that this fact can
be utilized to great advantage. There are
in the laboratory now, and have been for
number of years. the descendants Of a
tubercie germ which originally caused the
death Of guinea pigs in four to five weeks
after they had been inoculated. This
germ. which is now perfectly harmless,
was originally obtained from a specimen
OF tuberculous sputum. The guinea pigs
| fDocuiated with this sputum died in due
time from tuberculosis, and the cultures
| made from the diseased organs served as
starting point for a large and profic
family. By accustoming this germ grad
uaily to liquid food which had a slight acid
reaction, We eventually succeeded in elimi-
mating its ability to produce tuberculosis
wnen 1t was inoculated into animals.
Attenunted Cultures.
THE germs, however, did not lose the
property of producing or secrcting their
active poisons-thcse poisons which form
the active principle OF tuberculin. Gull
lures Of this sort, which have been caused
to lose their virulence or pathogenIc prop
critics. are called attenuated, and we have
used these attenuated cultures to great ad-
vantage since 1893. both in preparing tu-
berculin and in treating animals, or in
jecting animals for the purpose of pro-
tecting them against an incubation with
virulent tuberculosis or producing in them
a serum which may have curative proper
ties. Virulent cultures are also used in
preparing the tuberculin. and there are al
ways number of different generations Of
varying virulence of tubercle bacilli on
tand in the laboratory
When the tubercle cultures have grown
sufficiently, which requires from one montl:
to three months depending upon the readi-
ness with which the growth begins land
this is always Influenced by the rcaclicn
CT the media and the condition of the cul-
ture from which the inoculations are
made). the TASKS with their contents ere
removed from the incubator and placed
Immediately in the sterilizing oven, which
Is kept at a temperature Of about ,25 de-
erees cenusrade. The cultures are left
IN this oven until they begin to boil. In
this way the, germs are killed, and the
plugs in the mouth OF the TASKS NAV be
removed and the material filtered with
out any danger of injecting the workers.
VI course. in handling tubercie cultne3 in
such large uantities there is ALWAYS some
Danger OF Infection for :he people who are
doing the work. When proper care l. ,,s-
ed this danger is OF practically no i,nport.
ance; but as accidents may occur tasks
De oroken and their contehts spilled upon
tabies or fccr or in other places) IL is n
matter Of impossibility 10 avoid an dan
ger But the discovery that tile a,trnuot
ed germs can be used to advantage foI the
preparation of tuberculn materially re-
ducss the Possibility of danger II .ha work
ers in handling this material.
Alter heating the TASKS in the ster-
iiizer the cotton plugs are removed end the
contents Of the flask heated over = flame
germs. which are packed close together.
remain upon the filter paper and are wash.
ed once or twice with small amount of
water. The fltrate. including the wash
inss, Is then evaporated and may be con-
eentrated to any desired volume. As a
rule. one-fifth Of the quantity of the
original culture is the most convenient
point to be reached in the evaporation.
Instead OF fltering off the germs and then
evaporating the fltrate. the entire con-
tents of the flask may be concentrated by
evaporation and the solution filtered after
II has been concentrated. The results are
the same. but my preference is for the first
method.
Instead Of sending out concentrated tu-
berculin. 1t has been found advisable 10
dilute 1t to such a strength that two cubic
centimetres will be suitable dose for the
purpose of diagnosing tuberculosis in cat
tie. Several methods of Standardization of
the tuberculin are adopted"