Page 39 - My FlipBook

ject, trying to develop a means by which we could know
this subject better, and it will be my object this morning to
show you the means devised for developing a knowledge of
it. I do it, not so much as a matter of teaching the kine-
tics of the mallet in a scientific way, as to draw your at-
tention strongly to this subject of study experimentally and
to give you an insight into the possibiHties of study along
this line. I cannot take the time to enter into a lengthy
discussion upon the science of this subject now. I hope the
time wnll soon come when we will have a chair of physics as
applied in dentistry, in which every student can go into the
laboratory and study these things for himself, having the
necessary instruments and apparatus to do it. My presenta-
tion will be demonstrations rather than a lecture.
The study of hand pressure is comparatively easy and
many of you are acquainted with the instrument for that
purpose. This manudynamometer many of you have already
seen and have worked some with it. The senior class of last
year had a great deal of work with it. It was introduced
to\vard the middle of the term and used a great deal from
that time on. All that is necessary with this instrument is
to take the ordinary plugging instrument in the usual way
and make pressure, and the pencil flies forward and makes a
record of the number of pounds hand pressure. By studying
this, weighing your muscular effort, you will soon learn
what I mean by fifteen pounds pressure, or by ten or other
number of pounds pressure We can make such hand pres-
sure as we please, weighing our muscular effort and learn
to know the pounds value of the muscular effort that we use.
One may take a weight in the hand and heft it, as we say,
and come pretty close to the number of pounds in that
weight. If one makes an effort to become skilful in that he
may w^igh a piece of metal or other object very closely in-
deed. In this way, by experience with this instrument, we
may learn to know very well what is meant by so many
pounds hand pressure. Without some such means it is im-
possible for us to communicate intelfigently in regard to thiji
•matter. (Demonstrations.)
The study of mallet pressure is something very different
and much more difficult. Perhaps that is one reason why
we have more difficulty, more failures, more mistakes in the

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