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BIOLOGICAL STUDIES ON THE BACTERIA OF THE MOUTH. 97

destroyed l)v their own products, or finally they may enter upon
the state of spores.
It may, therefore, readily oecur that a putrid pulp does not
contain a single bacterium capaljle of development.
Of seventeen necrotic tooth-pulps which I have examined
Avith reference to this question, I found seven without living (at
least without cultivable) bacteria. Attention has already been
called to the tact that the dental pulp presents in a high degree
the conditions essential to the formation of spores; and since
spores possess high power of resistance, the antiseptic treatment
of root-caiials is thereby rendered more difficult.
In order to determine whether a necrotic pulp contains liA-ing
bacteria or not, we proceed in the following manner. Taking a
freshly extracted tooth (the best are such whose puli)-chambers
have not been opened), we first cleanse it by placing it for a
short time in a solution of sublimate 5:1000; then carefully
wash it with sterilized water to remove the sublimate, dry it
with sterilized paper, and split it with sterilized forceps. The
pul}) is then removed with a sterilized needle and brought into
the culture-medium, in which it is crushed, the solution being
repeatedly shaken in order to distribute the organisms e(pially
throughout. From this a second or even a third dilution is made,
and the number of colonies determined in the usual manner.
Experiments 1 to 5 were made on gelatine, the others on agar-
agar at a temperature from 37° to 38° C.
rom Pulp 1 . 4800 colonies developed.
2 • . 4800
3 235
4
5
6 275
7
8 3
9
10 • 4
11 . 250,000
-
12, dry. , black.
foul-smelling