It is to be noted that the Hunterian ligature does not aim at arresting the flow of blood through the sac, but is designed so to diminish its volume and force as to favour the deposition within the sac of laminated clot.  The development of the collateral circulation which follows upon ligation of the artery at a distance above the sac may be attended with just that amount of return stream which favours the deposit of laminated clot, and consequently the cure of the aneurysm; the return stream may, however, be so forcible as to prevent coagulation of the blood in the sac, or only to allow of the formation of a red thrombus which may in its turn be dispersed so that pulsation in the sac recurs.  This does not necessarily imply failure to cure, as the recurrent pulsation may only be temporary; the formation of laminated clot may ultimately take place and lead to consolidation of the aneurysm.

The least desirable result of the Hunterian ligature is met with in cases where, owing to widespread arterial disease, the collateral circulation does not develop and gangrene of the limb supervenes.

Anel’s ligature is only practised as part of the operation which deals with the sac directly.

Distal Ligation.—­The tying of the artery beyond the sac, or of its two branches where it bifurcates (Brasdor, 1760, and Wardrop, 1825), may arrest or only diminish the flow of blood through the sac.  It is less successful than the proximal ligature, and is therefore restricted to aneurysms so situated as not to be amenable to other methods; for example, in aneurysm of the common carotid near its origin, the artery may be ligated near its bifurcation, or in aneurysm of the innominate artery, the carotid and subclavian arteries are tied at the seat of election.

Compression.—­Digital compression of the feeding artery has been given up except as a preparation for operations on the sac with a view to favouring the development of a collateral circulation.

Macewen’s acupuncture or “needling" consists in passing one or more fine, highly tempered steel needles through the tissues overlying the aneurysm, and through its outer wall.  The needles are made to touch the opposite wall of the sac, and the pulsation of the aneurysm imparts a movement to them which causes them to scarify the inner surface of the sac.  White thrombus forms on the rough surface produced, and leads to further coagulation.  The needles may be left in position for some hours, being shifted from time to time, the projecting ends being surrounded with sterile gauze.

The Moore-Corradi method consists in introducing through the wall of the aneurysm a hollow insulated needle, through the lumen of which from 10 to 20 feet of highly drawn silver or other wire is passed into the sac, where it coils up into an open meshwork (Fig. 73).  The positive pole of a galvanic battery is attached to the wire, and the negative pole placed over the patient’s back.  A current, varying in strength from 20 to 70 milliamperes, is allowed to flow for about an hour.  The hollow needle is then withdrawn, but the wire is left in situ.  The results are somewhat similar to those obtained by needling, but the clot formed on the large coil of wire is more extensive.