Evening star., 1951-05-11
Dental Tests Show Man
Has q Double Mouth
Teeth Also Are Sense Organs
Like Eyes or Nose
By Thomos R. Henry

Man has double mouth.
Teeth are sense organs, like eyes or
nose.
These are two Of the findings Of re-
search enterprise sponsored by the
Office Of Naval Research at the Tufts
College Dental School, preliminary re-
suits Of which have been reported by
DIR. r. S. Manly.
Just as man has two hands and two
feet. the report says, it has been de-
termined that he has right and left
mouth for purposes of chewing. When
1t comes to such things as talking or
biting, the mouth becomes a single
organ once more and functions as
whole.
This long has been suspected, DR..
Manly says, from experiments on ami
mails. In such animals jaws can be
split in half, Then each part appears
to function independently Of the other.
It will clamp down when the teeth are
gently stroked and open when pain
full force is applied to teeth or gums.
Separate Nerve Supply.
Each side of the jaw has separate
and independent nerve supply. The jaw
must be swung slightly to the right or
the left to make the best contact be-
tween teeth on those sides. The ma
jority of persons, the research shows,
are right -jawed, just as they are right
handed. If, however, the teeth Of the
left jaw are in much better shape, per-
sons rather quickly adjust to the change
and become definitely left-jawed. usually
for the rest of their lives. Other tests
have shown that persons usually chew
more efficiently on the right when all
the teeth are normal unless they hap
pen to be born left-mouthed. This
does not necessarily accompany left
handedness or the rare tendency to use
the left eye more than the right eye.
The subjects were tested in chewing
peanuts, taken as fairly characteristic
of softer foods, and carrots represent
ing tougher foods. The thoroughness
with which these were ground in the
mouth was taken as a criterion.
One effect of the investigation may DO
a considerable revision Of military den-
tai standards. Possession of various pairs
Of teeth in good order is now prescribed.
Actually it makes great deal OF dlf1er-
ence whether all are on one side or
distributed between both sides, the re-
suits show. A great deal depends on
experience and the adaptability OF per-
sons who have lost teeth.
Sensitive Sense Organs.
A surprising finding was that the
teeth are extremely sensitive sense or
gans. Some of them, it was found, can
detect a touch Of tenth OF gram. A
molar can distinguish the weight OF
five grams, about that Of five-cent
piece The teeth distinguish the size
Of food morsels, giving cue as to what
should be swallowed. A series OF disks
of different thicknesses was held ous
before a person who was asked to oite
upon each and estimate its thickness.
It was found that the teeth alone
could distinguish difference OF Is OF
a millimeter, less than the thickness OF
a playing card.
The teeth also are keen distinguishes
of degrees Of hardness. Rubber workers
often bite on rubber sheets, as the
best method of determining whether
one is harder than another.
These sense faculties remain about
as intense as ever when the tissues
Immediately surrounding teeth are cut
away. This brings the conclusion that
the sense discrimination depends on
nerves in muscles and joints near the
teeth.