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INSTRUMENT GBASPS. 53

of the hand and is brought in opposition to the thumb. Its use
depends upon finding a suitable thumb-rest in the position of use.
This can be done many times in the front of the mouth, particu-
larly in using cleavers in stripping enamel from teeth in prepara-
tion for the bands for artificial crowns, and also a limited use of
it may be made in filling operations. This grasp should be cul-
tivated by every operator.
The palm thkust geasp. Figure 30, is now almost obsolete
in dental operations. It was much used before the advent of
cohesive gold in the heavier work of non-cohesive gold filling.
The instruments were made with large handles having a rounded
end to rest in the palm of the hand. It affords great power, but
is wanting in delicacy of touch or movement. It can not be used
to much advantage with our modern instruments, yet on occa-
sions demanding it one may use much more force in a thrust than
with the pen grasjj. Indeed most men can use as much as three
times the force of their pen-grasp thrust. Persons not realizing
this may do injury by using too much force when grasping an
instrument in this way. It is not suitable for any other move-
ment than the thrust.
FINGEK POWEK.
ILLUSTRATIONS: FIGURES 31-33.
The power exerted by the pen grasp is directly dependent
upon the ability of the person to so grasp the shaft of the instru-
ment as to prevent it from slipping in the fingers. In this the
placing of the instrument so that the pulpy portion of the thumb
and finger ends grasp it, is of principal importance. Pressure
of the instrument on the side of the finger gives some support
in movement, but very little increase of power over a grasp with
the forefinger and thumb alone. The power of the finger grasp
is, of course, the important feature of difference between men.
Few persons realize the difference that really exists between per-
sons in this respect. The range of difference between men in
power of thrust with the pen grasp runs from five to tliirty-five
pounds, with the average at about fifteen pounds, as shown by
numerous tests made at meetings of dentists. It seems very
curious to find large muscular men with feeble finger power, yet
a man's general muscular development is no index to his power
in handling delicate instruments.
Figure 31 represents the instrument, the dentist's manu-
dynamometer, designed by the author, with which these tests
are made. It is a registering spring scale of moderate delicacy,