Page 225 - My FlipBook

the same crackling sound if we notice carefully, and at the
moment that that occurs the meat will be crushed out from
between the occlusal surfaces of teeth and pass over the
axial surfaces. You see that pass out from between the teeth
there (demomstrating). This piece of meat is crushed at thir-
ty-five pounds ; that is, it requires thirty-five pounds to crush
it through, and yet it is a very tender piece of meat. Most
meats require a litle more than that ; most mutton chops
require thirty-five to forty pounds to crush the fiber. Now,
we can chew that very fine, if we choose, with this instru-
ment, but in doing that I am really putting on about sixty
pounds, and most persons will bring their teeth together
with a force of from seventy to ninety pounds in the ordi-
nary chewing of meat; that is, the teeth will dash right
throug-h it, and that is the proper way to chew meats. In
chewing meats the habit is the direct up and down motion;
very few people will chew meats with any other than the
straight up and down motion. All of the carnivorous ani-
mals have their jaws so fixed that they can use no other
motion, while the herbivorous animals have the lateral mo-
tions largely developed. We use the lateral motions in the
chewing of bread, and such articles as that ; indeed, we can-
not break up a piece of bread by the direct up and down
motion ; it will simply be packed between the cusps of the
teeth and will resist. My patients used to come to me and
say that they had broken this tooth or that — particularly
—
artificial teeth just biting a soft bread crust, and I used
to suppose that this was a misconception if not a down-
right falsehood. But when I undertook to experiment care-
fully upon the chewing of different articles of food I found
that of all things a comparatively soft bread crust was the
thing with which teeth might be broken, because I could
catch it between these teeth and bring the machine together
with a force of 240 pounds, and it would not be crushed out
from between the teeth, but would simply pack between:
the teeth and stay there. But by a little lateral motion it
goes to pieces. So that it is a substance well calculated
to break teeth ; it wedges between prominent cusps and
brings a splitting' force that is very powerful indeed. Now,
in the chewing of ordinary beefsteak the average will be
about sixty pounds upon two upper and two lower molar

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