the side of the
vessel by the probe or director, and, with the precaution of not
including the venal comites, the ligature may now be passed around the
vessel. In the lower third of the arm it is not likely that the operator
will encounter the ulnar nerve, and mistake it for the median, since the
former, d, Plate 16, is considerably removed from the vessel. If the
incision be made precisely in the usual course of the brachial artery,
the ulnar nerve will not show itself. It will be well, however, to bear
in mind the possible occurrence of some of those anomalies to that
normal relative position of the artery, the median, and the ulnar nerve,
which the accompanying Plates represent.

The median nerve, D, Plate 16, is sometimes found to lie beneath the
artery in the middle and lower third of the arm. At other times it is
found far removed to the inner side of the usual position of the vessel,
and lying in close contact with the ulnar nerve, d. Or the brachial
artery may take this latter position, while the median nerve stands
alone at the position of D, Plate 16. Or both the main artery and the
median nerve may course much to the inner side of the biceps muscle, A,
Plate 16, while in the usual situation of the nerve and vessel there is
only to be found a small arterial branch (the radial), which springs
from the brachial, high up in the arm. Or the nerve and vessel may be
lying concealed beneath a slip of the brachialis anticus muscle, E,
Plate 16, in which case no appearance of them will be at all manifested
through the usual place of incision made for the ligature of the
brachial vessel. Or, lastly, there may be found more arteries than the
single main brachial appearing at this place in the arm, and such
condition of a plurality of vessels occurs in consequence of a high
division of the brachial artery. Each of these variations from the
normal type is more or less frequent; and though it certainly is of
practical import to bear them in mind, still, as we never can foretell
their occurrence by a superficial examination of the limb, or pronounce
them to be present till we actually encounter them in operation, it is
only when we find them that we commence to reason upon the facts; but
even at this crisis the knowledge of their anatomy may prevent a
confusion of ideas.

That generalization of the facts of such anomalies as are liable to
occur to the normal character of the brachial artery, represented in
Plates 15 and 16