112

PATHOGENIC BACTERIA.

through. To be certain of the efficacy of such a filter
the fluid first passed through must be tested by cultiva-
tion methods. The complicated Pasteur-Chamberlaiid
and the simple Kitasato and Reich el filters are shown in
Figures 14, 15, and 16.

After having been used a porcelain filter must be dis-
infected, scrubbed, dried thoroughly, and then heated in
a Bunsen burner or blowpipe flame until all the organic
matter is consumed. In this firing process the filter first
turns black as the organic matter chars, then becomes
white as it is consumed. The greatest care must be
exercised in cleansing, and especially must care be taken
that the porcelain is dry before entering the fire, as It
will certainly crack if moist.

Before using a new filter it should be sterilized by dry
heat, then connected with receivers and tubes, also care-
fully sterilized. It should not be forgotten that the fil-
tered material is still a good culttire-medium and must be
handled with the greatest care.

While the filtration of water, peptone solution, and
bouillon is comparatively easy, gelatin and blood-serum
pass through with great difficulty, and speedily gum the
filter, so that it is useless until fired.

A convenient apparatus used by the author for the rapid
filtration of large quantities is shown in the accompany-
ing illustration (Fig. 17).

FIG. 17.—Apparatus for the rapid filtration of toxins, etc

The Disinfection of Instruments, Ligatures, Sutures,
the Hands, etc.—There are certain objects used by the