Page 270 - My FlipBook

242 THE MICRO-ORGANISMS OF THE HUMAN MOUTH.

border. "Within this zone the bacteria develop very slowly, so
that the cloudiness appears much later than on other parts of the
plate. The antiseptic action of Pack's pellets was particularly
marked. Pings of the unannealed pellets made in holes bored
in wood showed considerable action, even after they had lain for
forty-eight to seventy-two hours in a mixture of saliva and bread.
Also Abbey's soft foil and quarter-century foil showed similar
action, but in a somewhat less degree. Other preparations
showed varied effects ; some were almost or quite indifferent.
The antiseptic action was completely destroyed by annealing the gold
beforehand (Fig. 108). Some preparations of sponge gold and
platinum gold acted in a similar manner, and even old gold fill-
ings now and then showed considerable antiseptic action.
I shall not attempt to give any explanation for these facts now.
Different explanations suggest themselves, none, however, with
which I have been quite satisfied. Nor will I at present en-
deavor to answer the question whether the action is strong
enough to be entitled to any consideration as a saving property
of unannealed gold. I am inclined to think that it would be
rather venturesome to assert that it is.
Tin-gold was less active than gold alone.
I applied this method of testing the antiseptic property ot
filling-materials to a few other substances among them to iodo-
;
form, which did not have the slightest action in checking the
growth of the micro-organisms tested.
11.
In order to make a direct test of the action of fillings upon
carious dentine or upon the micro-organisms contained in it, we
proceed as follows A number of fi-eshly-extracted teeth which
:
are extensively decayed, not, however, so as to expose the pulp,
are cleansed of the remains of food, and only partially excavated,
so as to leave a thick layer of carious dentine in each cavity.
The cavities are then filled with various substances whose
antiseptic action we wish to test, and the teeth placed in a mix-
ture of saliva and bread and kept for three days at a tempera-
ture of 30° C. to 40° C. At the end of this time they are taken
out, wa'^hed in pure water, placed for a moment in sublimate