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HISTORY OF DENTAL SUKGERY 181

creasing, it will stand till tlie pressure reaches a varying amount, from, say
one liundred to seven hundred pounds, depending upon the alloy used and
tlie manner of making and packing the amalgam, and then it will crush and
fly in pieces. ]>Lit if the same amalgam hlock were placed wiiere a steady
pressure of no more than twenty-five pounds is constantly acting upon it
by means of a spring, the block will gradually spread and flatten so as to get
away from the pressure without breaking. This change is called flow and
may take place in the mouth under the repeated pressure or blows of mastica-
tion upon a filling, '.\iiialgam that flows under a pressure of fifty pounds is
unfit for fillings in occlusal surfaces on that account, aside from tlie accom-
panying shrinkage in such over tinned alloys."
This work with the amalgam alloys by Dr. Black was done so tiioroughly
and the demonstrations were so easily observed and readily comprehended that
there has resulted a very important improvement in the amalgam operations
of all intelligent and progressive practitioners.
Much laliorious and disinterested work was done by a considerable number
of persons from time to time in experimenting with amalgam alloys and test-
ing fillings, which want of sjiace forbids us to describe or enumerate. History
is chiefly conceriied with such scientific and experimental work as is brought
to a successful conclusion and results in beneficent changes in the practice of
the profession, rather than with the work, however sincere, tliat is inadequate
or unsuccessful to such a degree as to fail of any permanent or important
results.
THE NEW DEPARTURE.

What has been since known as tlie "new departure" was based on the
electro-chemical theory of decay and was for several years a subject of earnest
controversy which resulted in a large increase of the use of amalgam, gutta-
percha and the cements, and corresponding diminution of the use of gold for
filling teeth. A large numlier of good operators never accepted the new de-
parture creed, finding it impossible to reconcile its claims as to the be-
liavior of fillings with their clinical experience. After the true theory of the
etiology of caries was discovered and promulgated by Dr. W. D. Miller, of
Berlin, the controversy over the "now departure" creed gradually subsided,
though its influence can still be seen in the opinions and practice of many
good men throughout the country. This creed was announced in a paper by
J. Foster Flagg read before the Xew York Odontological Society in November,
1877. An editorial in the "Cosmos" for March, 1878 (Vol. XX, p. 174), pre-