TO />/t 774AM/AV/J THERMAL DKATH-rOINT. 177

removed as soon as it is certainly heated through, another
in five minutes, another in ten minutes, or at whatever
intervals the thought, and experience of the experimenter
shall suggest.

In both of the described procedures one must be care-
ful that the temperature in the test-tube is identical with
that of the water in the bath. There is no reason why a
sterile thermometer should not be placed in the heated
tube in the first case, and in the second experiment one
of the test-tubes exposed under conditions similar to the
others might contain a thermometer which would show
the temperature of the contents of the tube containing it,
and so be an index of the rest.

Another method of accomplishing the same end is to
use Sternherg\s bulbs. These are small glass bulbs
blown on one end of a piece of glass tubing, which is
subsequently drawn out to capillarity at the opposite end,
If such a bulb be heated, and its capillary tube dipped
into inoculated bouillon, in cooling, the fluid is drawn in
so as to fill it one-third or one-half. A number of these
tubes are filled in this manner with freshly inoculated
culture-medium and then floated, tube upward, upon
a water-bath whose temperature is gradually elevated,
the bulbs being removed from time to time as the
reqtiirecl temperatures are reached. Of course, as the
bulbs are already inoculated, all that 5s necessary is to
stand them aside* for a day or two, and observe whether
or not the bacteria grow, fudging the 'death-point exactly
as in the other case.

To Determine the Antiseptic and Cermicldal Value
of Reagents.—There are various methods whose modi-
fications can be elaborated according to the extent and
thoroughness of the investigation to be made.

I. T^he Antiseptic I *aht*\—'Remembering that an anti-
septic is a substance that inhibits bacterial growth, the
method that will at once suggest itself is that of adding
varying quantities of the antiseptic to be investigated to
culture-media in which the bacteria are subsequently

12