In the former instance, when a ligature is applied to the trunk of an artery, the supply of blood to the limb below it is interrupted for a few moments ; the aneurism loses its pulsa tion, and sinks and diminishes in size more or less according as its contents had been fluid or coagulated. Soon the blood begins to flow through the collateral branches, and enters the aneurismal sac also, but it passes into it slowly and without impetus, and no part of it is again forced back into the circulation. It coagulates and comes to press upon and close the ruptured vessel, which is soon obliterated by lymph, and in process of time becomes degenerated into little more than a ligamentous cord. A beau tiful illustration of this entire process was seen in Mr. Crampton's case` of ligature of the com mon iliac artery. The patient had two aneu risms, one of very large size at the groin, the other in the popliteal space of the same limb, firmer, and of much smaller dimension. A liga ture of catgut was placed round the common iliac, which either rotted or by some accident became detached on the sixth day : the pulsa tion returned in the larger tumour, which soon afterwards burst, and the patient perished. The sac of the popliteal aneurism being so much smaller had time to become perfectly filled with blood, which was there coagulated and firm. The ligature had accomplished all that was necessary for it, and the cure would have been complete even although the ligature had loosened—whilst the opposite was the fact with reference to the larger tumour.
Sometimes, soon after the ligature has been applied, pulsation reappears in the tumour. This must always be considered as an untoward circumstance, but does not necessarily involve the failure of the operation; for it may take place under two different conditions of the parts. 1. In aneurisms of very long standing, in situations where there is a free and extensive collateral circulation, probably increased by the pressure of the tumour. In these the pulsation does not return for some time after the vessel has been tied, and is never so strong as before the operation. It may continue for several days, but gradually diminishes in force, and at last ceases. The progress of the case then resembles that of the ordinary forms of the dis ease, except that in this the cure is much more protracted. Apparently, such was Sir A. Cooper's first successful case t of ligature of the common carotid artery, as also the case of carotid aneurism published in the fifth volume of the Dublin Hospital Reports.t It is not un likely that Mr. Turner's case of aneurism in the fore-arm, in which he secured both radial and ulnar arteries, was of a similar description also. 2. Where by an irregular distribution there exist two trunks in the limb, both con veying blood to the aneurismal tumour. Sir C. Bell had a case of popliteal aneurism in the Middlesex Hospital, in which, just below the origin of the profunda, the femoral artery divided into two branches of nearly equal size, which ran parallel to each other until • they arrived at the spot where the artery perforates the tendon of the triceps muscle, and there they united again. Only one of these was tied, and
although the pulsation in the tumour ceased for a moment, yet it soon returned, and never disappeared until the patient's death, which happened a few days afterwards, from erysipelas. A preparation of a similar distribution is pre served in the Museum of the Royal College of Surgeons in Dublin ;* and it is quite clear that where such exists in an aneurismatic limb, the securing of one of the trunks could produce no benefit.
It has been already stated that one of the effects of the ligature on an artery is the eventual obliteration of the entire calibre of the vessel between it and the nearest collateral branch at each side, and, therefore, it might be supposed that if it be tied immediately close beyond an aneurismal sac in such wise that no branch shall intervene between the cord and it, the whole of the canal to the next branch, in cluding the spot where the rupture had taken place, ought to become obliterated, and the aneurism thus be cured. This is the principle that led to the performance of the operation of tying the artery at the distal side of the aneu rism. It was (I believe) originally proposed by Delpech, and put in practice by Desault, but the termination of the case gave little en couragement for future trials, and it fell into disuse until of late years, when it has again been tried in England, and still subsequently by Mott, in New York, but not with a success to justify its general adoption. There is but one artery in the body (the common carotid) so circumstanced as to answer the design of the operation ; and even in this, if the smallest and most trifling branch happened to intervene be tween the aneurism and the ligature, it must defeat the principle of the operation altogether, and perhaps tend to aggravate the disease.
True different pathological conditions of an artery have been regarded as constituting this disease ; one in which the entire circumference of the vessel is distended, forming a tumour of an oval shape, pulsating strongly during life, and not containing coagu lated blood : the other is where all the coats of an artery at one particular spot are dilated in such wise as to form a sac springing from the side of the vessel, and containing blood with drawn from the circulation, and in a state of coagulation. Perhaps it would be more cor rect to regard the former of these as a state of vessel predisposing to the formation of a false aneurism, whilst the latter, presenting during life the same phenomena, and curable on the same principles that have been already laid down, must be considered as offering truly a specimen of the disease.