scapular, and
circumflex. These vessels, together with numerous smaller arteries,
appear to be confined to no fixed point of origin, and on this account
the place of election for passing a ligature around the main axillary
artery sufficiently removed from collateral branches must be always
doubtful. The subscapular artery, Q, Plate 12, is perhaps of all the
other branches that one which manifests the most permanent character;
its point of origin being in general opposite the interval between the
latissimus and sub-scapular muscles, but I have seen it arise from all
parts of the axillary main trunk. If it be required to give, in a
history of the arteries, a full account of all the deviations from the
so-called normal type to which these lesser branches here and elsewhere
are subject, such account can scarcely be said to be called for in this
place.

The form of the axillary space is conical, while the arm is abducted
from the side, and while the osseous and muscular structures remain
entire. The apex of the cone is formed at the root of the neck beneath
the clavicle, R, Plate 11, and the subclavious muscle, E, and between
the coracoid process, L*, of the scapula and the serratus magnus muscle,
as this lies upon the thoracic side; at this apex the subclavian
vessels, A B, enter the axillary space. The base of the cone is below,
looking towards the arm, and is formed in front by the pectoralis major,
K H, and behind by the latissimus dorsi, O, and teres muscles, P,
together with a dense thick fascia; at this base the axillary vessels, a
b, pass out to the arm, and become the brachial vessels, a*b*. The
anterior side of the cone is formed by the great pectoral muscle, H K,
Plate 11, and the lesser pectoral, L I. The inner side is formed by the
serratus magnus muscle, M, Plate 12, on the side of the thorax; the
external side is formed by the scapular and humeral insertion of the
subscapular muscle, the humerus and coraco-brachialis muscle; and the
posterior side is formed by the latissimus dorsi, the teres and body of
the subscapular muscle.

In this axillary region is contained a complicated mass of bloodvessels,
nerves, and lymphatic glands, surrounded by a large quantity of loose
cellular membrane and adipose tissue. All the arterial branches here
found are given off from the axillary artery; and the numerous veins
which accompany these branches enter the axillary vein. Nerves from
other sources besides those of the axi