ging along the acromial border of the artery, are a much
surer guide to the vessel.

On comparing the subclavian artery, at B, Plate 8, with the common
carotid artery, at A, Plate 7, I believe that the former will be found
to exhibit, on the whole a greater constancy in respect to the
following-mentioned condition--viz., a single main arterial trunk arches
over the first rib to pass beneath the middle of the clavicle, while the
carotid artery opposite the thyroid piece of the larynx is by no means
constantly single as a common carotid trunk. The place of division of
the common carotid is not definite, and, therefore, the precise
situation in the upper two-thirds of the neck, where it may present as a
single main vessel, cannot be predicted with certainty in the
undissected body. There is no other main artery of the body more liable
to variation than that known as external carotid. It is subject to as
many changes of character in respect to the place of its branching from
the common carotid, and also in regard to the number of its own
branches, as any of the lesser arteries of the system. It is but as an
aggregate of the branches of that main arterial trunk which ranges from
the carotid foramen of the temporal bone to the aorta; and, as a branch
of a larger vessel, it is, therefore, liable to spring from various
places of the principal trunk, just as we find to be the case with all
the other minor branches of the larger arteries. Its name, external
carotid, is as unfittingly applied to it, in comparison with the vessel
from which it springs, as the name external subclavian would be if
applied to the thyroid axis of the larger subclavian vessel. The
nomenclature of surgical anatomy does not, however, court a
philosophical inquiry into that propriety of speech which comparative
science demands, nor is it supposed to be necessary in a practical point
of view.

It will, however, sound more euphoneously with reason, and at the same
time, I believe, be found not altogether unrelated to the useful, if,
when such conditions as the "anomalies of form" present themselves, we
can advance an interpretation of the same, in addition to the dry record
of them as isolated facts. Comparative anatomy, which alone can furnish
these interpretations, will therefore prove to be no alien to the
practical, while it may lend explanation to those bizarreries which
impede the way of the anthropotomist. All the anomalies of form, both as
regards