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TEETH OF THE VERTEBRATA. 439
implanted in the premaxillary bones, which at an early period coalesce
with the maxillaries. Of these, the central pair is the larger and has a
slightly more anterior position than the lateral ones, on account of the
curve of the alveolar border. Their incisive nature is manifested by
the possession of a crown, which is bevelled on its palatine or lingual
surface ^ to a cutting edge, being broader at the extremity than at the
Fig. 216.
luferior Maxillary Bone of Man.
base. The adjacent teeth are in contact at their coronal extremities, but
on account of the narrower base a slight interval appears between them
at the margin of the gum. The root joins the crown without any
marked constriction, so that a neck can scarcely be said to exist ; from
this point it tapers gradually to an obtuse termination, being imperfectly
trihedral in form and slightly recurved.
In newly-erupted teeth the cutting edge of the crown is divided into
three inconspicuous cusps, which soon disappear through wear, leaving
it smooth. The basal termination of the crown is indicated by the limit
of the enamel covering, which is of greater vertical depth on the labial
and palatine or lingual than on the lateral faces, so that if a line be
drawn around the tooth at the most extreme basal portion of the
enamel, it will touch only the labial and palatine prolongations, and
not mark its exact limit on the mesial and distal surfaces. These
^ Tlie nomenclature of tlie various surfaces of a tooth as it stands in position in the
jaw, it seems to me, is simplified by employing terms with tlie following signification
if the tooth-line were straightened out upon each side, the surface which looks away
I'rom the condyle would be anterior, and that which is directed toward it would be pos-
ierior ; the surface directed toward the median line of the mouth would be internal, and
that directed away from it external. In this system some confusion may arise with
respect to the incisors and canines, in whicli tlie anterior surface is internal and con-
versely, owing to the curvature of tlie tootli-line ; but while it has appeared to me best
to speak of the surfaces as if tlie tooth-line were straight, I have in this paper adopted
terms now most familiar to the dental profession, which are represented by the follow-
ing: The sui-face looking toward the anterior part of the mouth and median line is
called the mesial surface; its opposite, looking toward tlie condyle, the distal surface.
In the superior row the surface which has been designated the internal I shall term
the palatal , and in the inferior row tlie lingual, while the external surface is the buccal
for the molars and bicusi)ids, and labial for the incisors and cuspids or canines.
The triturating surfaces of the molars and bicuspids are termed the masticating snrfiices,
while the incisive surfaces of the incisors and cuspids or canines are denominated the
catting edges.
TEETH OF THE VERTEBRATA. 439
implanted in the premaxillary bones, which at an early period coalesce
with the maxillaries. Of these, the central pair is the larger and has a
slightly more anterior position than the lateral ones, on account of the
curve of the alveolar border. Their incisive nature is manifested by
the possession of a crown, which is bevelled on its palatine or lingual
surface ^ to a cutting edge, being broader at the extremity than at the
Fig. 216.
luferior Maxillary Bone of Man.
base. The adjacent teeth are in contact at their coronal extremities, but
on account of the narrower base a slight interval appears between them
at the margin of the gum. The root joins the crown without any
marked constriction, so that a neck can scarcely be said to exist ; from
this point it tapers gradually to an obtuse termination, being imperfectly
trihedral in form and slightly recurved.
In newly-erupted teeth the cutting edge of the crown is divided into
three inconspicuous cusps, which soon disappear through wear, leaving
it smooth. The basal termination of the crown is indicated by the limit
of the enamel covering, which is of greater vertical depth on the labial
and palatine or lingual than on the lateral faces, so that if a line be
drawn around the tooth at the most extreme basal portion of the
enamel, it will touch only the labial and palatine prolongations, and
not mark its exact limit on the mesial and distal surfaces. These
^ Tlie nomenclature of tlie various surfaces of a tooth as it stands in position in the
jaw, it seems to me, is simplified by employing terms with tlie following signification
if the tooth-line were straightened out upon each side, the surface which looks away
I'rom the condyle would be anterior, and that which is directed toward it would be pos-
ierior ; the surface directed toward the median line of the mouth would be internal, and
that directed away from it external. In this system some confusion may arise with
respect to the incisors and canines, in whicli tlie anterior surface is internal and con-
versely, owing to the curvature of tlie tootli-line ; but while it has appeared to me best
to speak of the surfaces as if tlie tooth-line were straight, I have in this paper adopted
terms now most familiar to the dental profession, which are represented by the follow-
ing: The sui-face looking toward the anterior part of the mouth and median line is
called the mesial surface; its opposite, looking toward tlie condyle, the distal surface.
In the superior row the surface which has been designated the internal I shall term
the palatal , and in the inferior row tlie lingual, while the external surface is the buccal
for the molars and bicusi)ids, and labial for the incisors and cuspids or canines.
The triturating surfaces of the molars and bicuspids are termed the masticating snrfiices,
while the incisive surfaces of the incisors and cuspids or canines are denominated the
catting edges.
