New-York tribune., 1909-01-24
TEETH ARE NOT BONES
Variety of Form Which Adapts
Them for Varying Uses.

Familiar to everybody the teeth. few per
sons those who have dipped into their his
tory viewed from the scientific side, can form an
adequate idea regarding their true nature. II the
man in the street were asked construct cias-
sifed list Of his bodily belongings, he would al
most certainly place teeth III the section which
included the bones There appears reason for his
choice. Teeth hard and bonelike in structure.
and they are fixed in the jaws. These facts would
seem, on the face of things justify the tn
cIusion OF the teeth IN the list Of seetsl struct-
ures This view Of the teeth. however. IS readily
proved 10 be Incorrect We have only to appeal
TO natures way Of making tooth-in other words
to study its deveiopment-to assure ourselves tnat
teeth are not bones all but structures of
very different kind.
The first Indication OF tooth formation begins IN
very early life with the formation Of groove IN
the gum, or mucous membrane. lining the mouth
This f,1rrow is the birthplacs OF the teeth. From
the groove arises as many little projections OK
the gum there to be teeth Each protec-
ton call papilla- Now, this little body con-
tains plentiful supply OF blood vessels destined
to bring it the material -hlood-out OF
which not teeth alone all other organs. tissues
and secretions manufactured The pspilla. be-
Sides is composed of. and particularly invested
WITH living cells OF special kind These cshs are
TO be regarded as the workmen which fabricats
the tooth. The material specially required for
tooth formation consists Of compounds OF limss
associated with other substances
Around the papilIa and upon IL mould.
dePOsA4oa-
elaborated into substance which. under the micro
scope shows a special structure Of its OWE, dif-
fering widely from that which Is represented IN
bone The great bulk Of tooth consists OF ivory
dentine. It is also called This = dense.
hard substance. which shows texture composed
of an infinite variety microscopic tubules- But
at the crown Of the tooth especially We meet with
a layer OF different kind and OF still harder con-
sistence This is the enamel. which ranks as the
hardest substance in the body Its position on the
crown of the tooth bears relation 20 the resist
ance to wear and the tooth Is intended TO ex-
hibit the softer ivory being thus protected froD
the obvious results Of the process OF atttion- mus.
on the papiIla as living mould, the tootn II
formed its substance coming to cover. as IN an
envelope the little projection itself
Long before the tooth, however, Is completed, the
groove in the gum has become paruuoned on into
series of sacs or compartments The furrow it.
sA,f becomes converted into a tube by the upward
growth and union of its edges in the middle hne-
Then succeeds division into sacs, in each OF "niea
a papiiia is present, and IN each OF which' de-
veoping tooth is contained II the hard Inaterias
of the tooth be found around the paptla We dis-
cover thus that the tooth Is hollow. and not a
solid structure For the pulp inside every tooth.
a substance richly supplied with nerves and oiood
vessels re4IIy represents the papiia OF the carry
sta~ss The tooth's nourishHlent is thus duly pro-
vided for since processes Of the pulp pass INTO
the minute tubules Of the ivory. and so eontrouts
10 the maintenance of the vitality or tne orsaA-
when the tooth is completed within its sac all that
remains is for IL 10 appear N Iilo Jo"' -. -
provision has been made for Its nxauon A t0oen
.cuts'. the gum when. through upward pressurs
- the sac II bursts through its investment and
taxes the place nature has mapped out for II IN the
arrnamentarium Of the mouth
Now in ali this history there is no hint gwen
us of any connection between bone formation and
tooth development. save indeed for the connection
between the two structures in the Jaw The gum
;s the present tissue OF the teeth. and the gum
is simply the skin layer OF the body folded Inward
at the mouth TO form the lining membrane OF that
cavity. while II is continued onward, with varia-
tions in it's organization. form the lining OF tne
digestive tubes as we'll Teeth are therefore truly
Lir strct,res in respect of their mode OF origin.
which after ALL is the surest and indeed the only
test o- the nature Of any living tissue or part
By all odds the very longest tooth in the world
Is that OF the narwhal, which grows into twisted
ivory pole often exceeding six feet IN lensth-Aa-
drew, wilson In The Illustrated London NeuA