Omaha daily bee., 1911-12-16
POWER OF HUMAN JAWS
strength Exerted by Muscles and
MOlars in Chewing an Ordi-
nary steak.

A ten-pound bite requires a forty-pound
contraction of the human jaw muscles
That is because the jaws are built on the
principle of a pair OF tongs, The power
is applied near the joint, while the work
is performed at the opposite extremity Of
the jaw levers. Had a mechanical engi-
neer designed the human frame he would,
no doubt, have built the jaws after the
fashion Of nut cracker, with the mus
cles placed at the ends OF the jaw levers,
and the teeth between these ends and the
Joint or fulcrum, so that a powerful bite
could be obtained with very small OK
penditure of muscular effort. However, in
the physiology OF man and all other,a ami
NAL life. for that matter. mechanical ad-
vantage weighs for little in the presence
of other broader considerations. This is
why nearly all the principal muscles Of
the body must be far more powerful than
would be necessary were they to act d.
rectIy upon the work. When chewing we
have an almost direct application of the
power of the muscles as they nearly
overlie the third molaTs. There is a vast
difference between chewing and biting.
In order to determine the average
strength of the jaws, DIR. q. Il. Black,
president OF the Chicago Dental univer-
sity, sometime ago devised an instrument
of very simple design, but with name
that would put the average jaw to Sc
we're test-the gnathodynamometer, With
this instrument he made gnathodyna-
mometric tests of the jaws Of 1000 per-
sons. They were selected at random and
probably represent a good average OF
! civilized people. lie found that the limit
OF the bite was not determined by the
muscles but by the teeth themselves. In
nearly every case the patient would cease
his efforts, owing to the fact that his
| teeth hurt. This would depend largely
upon the condition OF the peridenial mem
| branes, and upon the habits Of the pa
tient I'm accustomng his teeth more or
| less TO chewing hard foods. The average
of the 600 persons showed III pounds for
the molar teeth and much less for bicus-
pids and incisors. out OF the 1000 per-
sons, seventeen developed force equal
to the full registry Of the instrument,
which was 275 pounds,
In a recent publication DIR. Black has
tabulated the records OF about fifty per-
sons who were tested with the gnathody-
namometer The list includes men and
women OF all classes, from a blacksmith
to Chinese laundryman, and from a
servant girl to a music teacher. II IL
natural 10 picture butcher as a man
with a well-develOped and powerful jaw
but among the patients I'm the list the
butcher showed a power Of only l65
pounds with his molars. from which we
may infer that he IL accustomed 10 Sc
lecting the tender meats for use on his
own table. The man with the highest
record was a printer, who registered HO
pounds (but any cOmpositof will admit
that printers pi is tough). while the sec
ond hOnors wentA to a dentist with 240
pounds. Among the women the highest
record reached was 100 pounds, while the
lowest was fOrty-five. Strangely enough
the schoolgirl who made the latter record
was able TO register seventy pounds with
her incisOrs, which might indicate that
she had accustomed her dental mem
branes of tho front teeth to harder work
by biting a pencil. or something OF the
Eort At any rate. she was one OF those
unnOrtunates who bite Off more than
they can chew" In this list OF records
males showed an averase OF iio pounds
With tho m0IsTs and eiKhty-three with the
ineisOrs. and females NJ pounds with the
mOlarA and nfty-ssven with inalsoCz,-
ssisntinc AmsFicNn