ular attachments.

H. Left sterno-hyoid muscle, cut.

I. Left sterno-thyroid muscle, cut.

K. Right sterno-hyoid muscle.

L. Right sterno-mastoid muscle.

M. Trachea.

N. Projection of the thyroid cartilage.

O. Place of division of common carotid.

P. Place where the subclavian artery passes beneath the clavicle.

Q. Sternal end of the left clavicle.

[Illustration: Neck and upper chest, showing blood vessels, muscles and
other internal organs.]
Plate 10

COMMENTARY ON PLATES 11 & 12.

THE SURGICAL DISSECTION OF THE AXILLARY AND BRACHIAL REGIONS,
DISPLAYING THE RELATIVE ORDER OF THEIR CONTAINED PARTS.

All surgical regions have only artificial boundaries; and these, as
might be expected, do not express the same meaning while viewed from
more points than one. These very boundaries themselves, being moveable
parts, must accordingly influence the relative position of the
structures which they bound, and thus either include within or exclude
from the particular region those structures wholly or in part which are
said to be proper to it. Of this kind of conventional surgical boundary
the moveable clavicle is an example; and the bloodvessels which it
overarches manifest consequently neither termination nor origin except
artificially from the fixed position which the bone, R, assumes, as in
Plate 11, or c*, Plate 12. In this position of the arm in relation to
the trunk, the subclavian artery, B, terminates at the point where,
properly speaking, it first takes its name; and from this point to the
posterior fold of the axilla formed by the latissimus dorsi muscle, O,
Plate 11, N, Plate 12, and the anterior fold formed by the great
pectoral muscle, K, Plate 11, I, Plate 12, the continuation of the
subclavian artery is named axillary. From the posterior fold of the
axilla, O P, Plate 11, to the bend of the elbow, the same main vessels
take the name of brachial.

When the axillary space is cut into from the forepart through the great
pectoral muscle, H K, Plate 11, and beneath this through the lesser
pectoral muscle, L I, together with the fascial processes which invest
these muscles anteriorly and posteriorly, the main bloodvessels and
nerves which traverse this space are displayed, holding in general that
relative position which they exhibit in Plate 11. These vessels, with
their accompanying nerves, will be seen continued from those of the
neck; and thus may be attained in one view a comparative estimat