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THE CONTOURING APPARATUS. 833

of traction force from molar anchorages ; the protrusion not being so
pronounced as to demand the use of the skull-cap.
It will be seen by the canine eminences—though far better shown
upon the model itself—that the position of the canine crowns is imme-
diately over the former alveoli of the first bicuspids. As they continue
to grow dowuAvard in this somewhat open channel, their roots, which
are not at present developed, will grow upward, the teeth in their en-
tirety finally taking a position and inclination similar to that of the
bicuspids which they replace, and considerably posterior to that which
they were otherwise destined to occupy.
The patient, nine years of age, had the teeth, eyes, ears, and general
temperament of the father, whose upper arch was abnormally protruded
in a similar manner, which was the raison cVctrc for dental aid.
Had the father's teeth been in proper relative and symmetrical
position, and similar to the son's in other particulars which could be
legitimately used as data, it would have been an argument in favor
of non-extraction with the expectation of other treatment later ; but
it should not have been passed upon without seeing the mother. Had
the mother's teeth been found small and the general physical features
cast in a more delicate mould than her husband's, investigations along
other lines would have been required with the view of determining
if the child had not the large teeth of the father and small jaws of the
mother ; in which case extraction would also have been indicated.
VI. The Contouring Apparatus.

The limited area upon which force can be applied to a tooth, com-
pared with that portion covered by the gum and imbedded in a bony
socket, has made it next to impossible, with all ordinary methods, to
move the apex of the root in the direction of the applied force ; nor
could this ever be accomplished with force exerted in the usual way at
one point upon the crown, however near the margin of the gum it may
be applied, for the opposing margin of the alveolar socket must receive
the greater portion of this direct force, and in proportion to its resist-
ance it will become a fulcrum exerting a tendency to move the apex of
the root in the opposite direction.
But if in the construction of the apparatus a static fulcrum is created
independent of the alveolar process at a point near the occluding portion
of the crown, while the power is applied at a point as ftir upon the root
as the mechanical and other opportunities of the case will permit, the
apparatus becomes a lever of the third kind, tlie power being directed
to a movement of the entire root in the direction of the applied force.
This proposition is made plain by reference to diagrams. In Fig.
891 let A be a point upon a central incisor at which force is applied in
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