than if the ligature be applied below those
branches. Hence, therefore, when the axillary artery is affected with
aneurism, thereby rendering it unsafe to apply a ligature to this
vessel, it becomes not only pathologically, but anatomically, the more
prudent measure to tie the subclavian immediately above the clavicle.

XVI.--The brachial artery, When this artery is tied immediately below
the axilla, the collateral circulation will be weakly maintained, in
consequence of the small number of anastomosing branches arising from it
above and below the seat of the ligature. The two circumflex humeri
alone send down branches to inosculate with the small muscular offsets
from the middle of the brachial artery. When tied in the middle of the
arm between the origins of the superior and inferior profunda arteries,
the collateral circulation will depend chiefly upon the anastomosis of
the former vessel with the recurrent branch of the radial, and of
muscular branches with each other. When the ligature is applied to the
lower third of the vessel, the collateral circulation will be
comparatively free through the anastomoses of the two profundi and
anastomotic branches with the radial, interosseous, and ulnar recurrent
branches. If the artery happen to divide in the upper part of the arm
into either of the branches of the forearm, or into all three, a
ligature applied to any one of them will, of course, be insufficient to
arrest the direct circulation through the forearm, if this be the object
in view.

XVII.--The radial artery. If this vessel be tied in any part of its
course, the collateral circulation will depend principally upon the free
communications between it and the ulnar, through the medium of the
superficial and deep palmar arches and those of the branches derived
from both vessels, and from the two interossei distributed to the
fingers and back of the hand.

XVIII.--The ulnar artery. When this vessel is tied, the collateral
circulation will depend upon the anastomosis of the palmar arches, as in
the case last mentioned. While the radial, ulnar, and interosseous
arteries spring from the same main vessel, and are continuous with each
other in the hand, they represent the condition of a circle of which,
when either side is tied, the blood will pass in a current of almost
equal strength towards the seat of the ligature from above and below--a
circumstance which renders it necessary to tie both ends of the vessel
in cases