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28 MAcnosroi'/c axatomy of the human teeth.

marked. In tlic latci'al iiicisoi- the lossa is often more marked and
the marginal )'ido-es more distinct.
The //;r.s/<^/and (fixfal sides are of wedge-like form, straight from edge
to cervix and widening in the same direction. A depression runs across
the neck just above the enamel line.
The neck is much compressed disto-mesially, and the root ])artakes
of this flattening through its entire length. The section presents a
compressed oval {e). The enamel line dips downward on the labial and
lingual sides, and curves upward on the UK^sial and distal, in a manner
characteristic of the incisors.
The edge is perfectly straight from side to side, after the three tuber-
cles, found when first erupted, are worn olf.
The root is flattened like the neck, and frequently a groove runs the
entire length on the mesial and distal sides. Occasionally complete
bifurcation results, which recalls the form of this tooth found in lower
animals.
The pulp canal (e) is of similar form to the root, and is flattened
and thin, so that it is often difficult to effect an entrance to it with
.
instruments.
The lateral is similar in form to the central incisor, but is wider at
the edge and the distal corner of the edge is slightly rounded (d). In all
other features it resembles the central incisor.

The Canines or Cuspids.
10. The Upper Canine.—This is the third tooth from the median
line and a])proxiniates the lateral incisor on its distal side. It is the
first tooth ])osterior to the intermaxillary suture and is imbedded in
the maxilla proper. It is commonly said to form the spring of the
arch, and conveys the impression of great strength, as is indicated by
its strong implantation. It is more strongly implanted, and by a longer
and larger root, than any of the other teeth. Zoologically it is the
largest tooth in the dental series, but in man is much reduced from
its prototype, the larger carnassial canine of lower animals, especially
the carnivora. It is the principal prehensile tooth, and is therefore
first in order of function in the dental series.
The canine in man preserves the typal form, for its mechanical
structure is still that of a single cone, brought to a point (Fig.
15, a). This is the earliest form of teeth found in the lower verte-
brates, the fishes and reptiles, which present only simple conical teeth
in all parts of the jaw. It has an older history than any other tooth,
and still bears the marks of the many changes through whicli it has
passed in the course of its evolution.