New-York tribune. [volume] (New York [N.Y.]) 1866-1924, 1910-07-03

Black Lnrerstys
Surprising Figures Der1ced from Series Of Experiments
Lasting Serenteen Years.

Do you know that il is impossibiIity to
bite the bread that mother makes? An absurd
question, you reply. But if you think you can
thrust your teeth through the particles of fluffy
wheat bread you make one Of the greatest mis-
t1kes Of your life. Such is Of the latest dis
coveries Of science, announced a result Of a
series Of tests made to determine the amount
Of pressure exerted by the human jaw in the
process Of nasticating food
Do YOU know that the woman who particl-
pates il the ordinary conversation Of the gossip
fest shuts her jaws together with force OF
sixty pounds every time she utters a syllable,
while a man in vehement oratory makes teeth
crash against teeth with one-hundred- pound
blows
Dr. Greene Vardiman Black is the man who
does know. Ee is the dean Of Northwestern
University's dental school in Chicago For
seventeen years he has been testing the strength
q the muscles Of the human jaw to ascertain
how hard men and women bite OF late he has
directed his experiments TO the number Of
pounds pressure exerted by the lower jaw IN
The mastication Of different kinds Of food.
The earlier experiments were carried on by
means OF the gnathodynanomete-, which DR..
Black invented This resembles a pair Of pliers
about FIVE inches long. The jaws Of the device
are held open by apparatus similar to that OF
q spring scale, which is incIosed between what
might be termed the handles Of the pliers To
this apparatus is attached a pointer that reg
listers the number Of pounds pressure exerted
on the jaws Of the instrument il closing or
partly closing them The test with this instru-
inert is simple. The subject opens his mouth
ha-f 70 three-Quarters Of an inch. enough TO ad-
Kit the insertion Of the jaws between his teeth,
then bites as hard as he can on the jaws Of the
nathodynamometer, which covered with
hard rubber for the protection Of the teeth The
pointer denotes the number Of pounds pressure
ezerted, just as a pair Of scales indicates the
weight Of pound Of sugar at the Custom House
eince the government investigation began there
With class Of six students Professor Black
obtained results showing wide differences in the
power Of the muscles to close the human jaws
One student registered 80 pounds pressure,
another 80 q third 1870 the fourth 10. the
ffta 225 and the sixth go pounds In tests
with ether classes there were subjects whose
rnazimum pressure was as low az 1Oo and as
high as 300 pounds. One student brought the
Jaws Of the gnathodynamoneter together with
snap repeatedly. The instrument be used, the
only one available at the time, had maximum
capacity Of 80 pounds. The ease and rapidly
with which he closed Il convinced Professor
Black that his jaw muscles We're capable OF at
q feature OF these tests which surprised e1-
pe-ts in anatomy was that the shape OF the jaw
and the physical appearance Of the subject
proved guide in guessing at the strength OF
the bite. The common impression was that the
Square jawed" man would do best Professor
Black found tha: the mainland the woman as
Eel-whose jaw bones We're not square" often
gave the stronger bite
AL these tests and many others OF the same
kind had z specific object relating TO the con-
strUction OF false teeth and the filling Of nat
Ural ones In fact, il was in fUrtherance of the
Investigated the subject at ALL and the same
purpose led him Oh to the study Of the pressure
c. the jaws in the processes Of nlastication and
Conversation To obtain definite results he in
vented the phagodynan1orneter. or chewing ma
chine. In q general way this Is like the Sna-
thocynamoneter but is more intricate 1t Is
designed TO record the pressure employed in eat
Ing without interfering with the natural mo-
ton Of the under Jaw. In the tests made with
this DR.. Black ascertained that the pressure re-
CURED TO rasticate beefsteak-the thick, juicy
cut that makes your mouth water as ii Hes
eseaning the platter-ranges from forty tc
sixty pounds. What is commonly accepted-oi
Rather rejected-as tough steak can be masli-
Gated only with the exertion Of sixty to eighty
pounds Of pressure
Pork chops are eaten with the greatest ease
Il takes q pressure of only 30 TO % pounds TO
bite through this deIicacy To maSticate NUT