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INSTRUMENT GBASPS. 55

that the power of thrust is rapidly diminished. A larger size
than one-fourth inch gives no advantage. This is the rigorous
conclusion after witnessing trials of different sizes of instru-
ment handles hy many men.
A study of the instrument grasps in the illustrations of fin-
ger and instrument positions will do much to enable one to form
correct conceptions of them. The positions assumed at the
chair are more natural than those assumed in trials on the manu-
dyiiamometer. Among these will be found a few illustrations in
which the grasp is put at ease as in doing some very light
manipulative work. In this the instrument is often shifted to
the true pen grasp with the shaft crossing the nail of the second
finger.
Ten years of exact observation of the finger power of den-
tists is not sufficient time to give very reliable historical data of
the variations that will occur in averages by practitioners because
of different methods of practice with different forms of instru-
ments and varying habits of manipulation. Only a few trials
of the power used by men in filling teeth are on record and these
are too vague to be regarded as giving definite information.
Somewhere the late Jonathan Taft has said that, with the old
large-handled instruments used in making fillings with non-
cohesive gold, he used as much as seventy-five pounds pressure.
He complained that this work was very hard on the muscles of
the chest. But the method of weighing was not given. Only a
few remarks of this kind can be gathered from our literature.
It was common in filling with non-cohesive gold to use the palm
thrust grasp, as shown in Figure 30. With this grasp and such
an instrument handle, the exertion of such force was possible.
Indeed, the full power of the arm could be used. We now know
also that such force properly applied would be readily borne by
the molar teeth of persons whose habits of chewing food were
good. There is much evidence that in the days in which much of
filling teeth was done with non-cohesive gold, using hand pressure,
and particularly in the latter part of that period when the smaller
instrument handles of modern times were used, men exerted
much more force than now in filling teeth. That is, fifty to sev-
enty-five years ago. This was continued by many into the cohe-
sive gold work. In my first trials of the registering of the hand
force used by men in dental association meetings, I noticed that
the older men, who had their first training in non-cohesive gold
work, were giving, on the average, the highest records. This has
continued, and, as these men drop away, the average of the