gradually deposited in the sac, which continues until the sac becomes filled, and no longer permits of the entrance of blood. I have next to show that the ulterior changes which take place are the same in both.

When the sac of an aneurism has been completely filled by fibrine, deposited as already mentioned, the disease is cured; it can neither increase in size, nor can rupture take place. If the aneurism was seated in the arch of the aorta, however, the calibre of the artery at the part from which it springs will still be preserved, and the circulation will continue through it as before, because the anastomosing branches are not sufficiently numerous or large here to carry on the circulation if this vessel was suddenly obliterated; while the current through it is necessarily too strong to permit of fibrine being deposited in its interior. Eventually, the sac diminishes in size from the gra dual absorption of its contents, and ultimately it may in a great mea sure disappear.

When the sac of an external aneurism has become filled by fibrine, the disease is evidently also cured, and the circulation through the artery may continue for a time; but the anastomosing branches here being numerous and free, the blood passes down the main artery of the limb in a diminished stream, the deposition of fibrine therefore continues until the artery at the seat of the aneurism is encroached upon and gradually filled by fibrine, when its pulsation stops, and the deposition of fibrine ceases.

Once a certain amount of fibrine has been deposited in an aneurismal sac, as the result of pressure upon the artery above, there would appear to be an irresistible tendency to its continuing to be deposited until the artery at the part is likewise closed up; this fact has been proved by the two cases to which I have recently referred, where the patients refused to continue the pressure, and commenced taking exercise; yet under these apparently unfavourable circumstances, the pulsation ceased after a short interval, and a cure was effected. It is therefore not unlikely that the artery has many times been tied in aneurism, where the process which nature sets up for its cure had made considerable progress, and where a little further delay would probably have done away with the necessity for its performance.

The ultimate changes which take place when the pulsation of an external aneurism ceases, are the same, whether this result has occurred spontaneously or been brought about by compression. The circulation is carried on by the enlarged collateral vessels, the contents of the sac and the artery at the part from which it springs, are gradually removed by the absorbents, the sac disappears in a great measure, and the vessel is eventually converted into an impervious ligamentous band. Guattani Petit, besides many other writers, have reported cases of aneurism spontaneously cured, where this condition of the parts was found; and I have already described the appearance which I found in a case were the patient died two years and a half after the cure of a popliteal aneurism by compression, and sixteen months after the cure of a femoral aneurism in the opposite limb;

"the artery at the site of each anurismal sac was converted into a solid, thick, ligamentous band, its channel was obliterated, and the contents of the sacs had been removed by the absorbents."

The foregoing facts all go to prove, that when a cure of external aneurism takes place spontaneously, or when it is brought about by compression, it cannot fail of being permanent; the sac is filled up, and the artery from which it springs is obliterated; consequently, pulsation cannot return, nor can a secondary aneurism form at the part, both of which have occasionally occurred after an apparent cure by the ligature.

Proofs that the ligature at a distance from the sac effects the cure of aneurism in the same way as compression.

I have now given a sufficient number of proofs that the mode in which compression effects the cure of aneurism, is identical with that by which nature accomplishes this object. If it could now be shown that the ligature of the artery at a distance from the sac generally effects the cure of aneurism in the same way, it might help to remove the prejudiced view taken of compression by surgeons, who are either so wedded to the ligature that they distrust every other mode of treating aneurism; or who, through ignorance of the principles upon which it effects a cure, can see in it nothing but the revival of an obsolete and abandoned method. This I shall now endeavour to do.

Almost every writer upon aneurism mentions cases where the pulsation returned after the ligature had been used; or where hæmorrhage occurred from the sac subsequent to the operation. "It is not uncommon (Mr. Guthrie says) for a pulsation to be felt in the tumour a few hours, or in a day or two after the operation, but it very rarely continues." "A stream of blood (Mr. Hodgson observes) in most instances passes through the aneurism after the ligature of the su perior part of the artery; yet this current is in most instances not sufficient, either by its quantity or by the force with which it is impelled, to continue the disease."

These facts show that the ligature of the artery at a distance from the aneurism does not always prevent a current of blood from passing through the sac, while pathology proves that inosculating branches not unfrequently communicate with the artery between the ligature and the sac; that the artery is always pervious here, and remains so after the cure of the aneurism; and that the sac has been found filled with fibrine deposited in concentric layers, where an opportunity has been afforded for examining the limb some time after the operation. The theory laid down in modern works respecting the node in which the ligature of the artery at a distance from the sac effects the cure of aneurism, is as follows:-When the ligature is tightened, the blood contained in the sac, or which may find its way into it afterwards, distends the sac, and extends into the artery above and below the opening by which it communicates with it; it coagulates, the fluid parts are absorbed, and the more solid, aided by the contraction of the sac, form a firm tumour. The coagulum is subsequently removed by the absorbents, and the vessel is obliterated at the seat of

The sac

the aneurism, and for a short distance above and below it. gradually diminishes in size from the absorption of its contents, and ultimately disappears either wholly or partially.

The foregoing theory would be perfectly correct if the artery were always tied close to the aneurismal sac, or if the artery were always obliterated between the ligature and the sac. But as the ligature is applied at a distance from the sac, and as the vessel in nineteen cases out of twenty remains pervious afterwards for some space between the ligature and the sac, it is evident that the vessel here must have continued to convey blood after the operation, because otherwise its cavity would eventually have been obliterated. It is therefore probable that a feeble current of blood continues to pass through the sac after the operation, and that in a great majority of cases the cure is brought about by the deposition of fibrine in the sac, not by the coagulation of its contents. This is further confirmed by pathology; Mr. Hodgson says, "in the dissection of cases some time after the operation, it has been found that the cavity of the sac was filled with concentric layers of coagulum, similar to that which is met with in aneurisms undergoing spontaneous cure," which obviously could not have occurred unless a current of blood continued to pass through the sac after the operation.

The ligature of the artery at a distance from the sac cannot of course effect the cure of aneurism unless the sac itself becomes obliterated now, it appears to me that if the theory usually laid down were correct-viz., that the blood contained in the sac, and that which finds its way into it subsequently, coagulates after the ligature is tightened, one of two results would follow the operation much more frequently a secondary aneurism would form at the part or suppuration of the sac would ensue.

A secondary aneurism, for instance, would be liable to form, if the sac was large, and its contents wholly fluid at the time of the operation. It is obvious that in such a case, when the fluid portion of the coagulum is absorbed, the sac must shrink considerably to form a solid tumour. Writers upon aneurism have, however, endowed aneurismal sacs with extraordinary elastic powers, in order to enable them to uphold this theory; but in all the cases which I have seen dissected, the sac had formed adhesions with the parts in its vicinity; and if it possessed elasticity (which, considering that it is composed of the cellular coat of the artery is rather doubtful,) this agent could not have come into operation; consequently if a large anastomosing branch eventually communicated with the artery between the ligature and the sac, the pulsation would return, and a secondary aneurism would form at the part. I have little doubt that in the cases which have been reported where this result followed the operation, it was owing to a coagulum only having formed in the sac; it evidently could not have occurred if the sac was filled by fibrine deposited in the way that had been mentioned.

That suppuration of the sac would be liable to ensue under such circumstances, is, I think, also evident. We have a large sac contain

ing more or less coagulated blood, this after a time comes to act as a foreign body, inflammation followed by suppuration sets in, particu larly if, as not unfrequently happens in hospital practice, the tumour is much or often handled. The history of operative surgery contains many cases where suppuration of the sac followed the operation; and what has now been said will explain why it should have occurred in some cases and not in others apparently similar. If the ligature is placed very close to the sac, and the current of blood is thus completely cut off from it, inflammation followed by suppuration is more liable to follow than where the vessel is tied at a distance from the sac; we have seen that in the latter case a feeble current continues to pass through the sac after the operation, the sac becomes eventually filled with fibrine, and inflammation is as unlikely to ensue as after the treatment by compression.

Writers upon aneurism are somewhat obscure as to the exact mode in which the artery at the seat of an aneurism is obliterated after the ligature. The examination of cases where the patient lived for a long time after the operation, proved that this did occur; and that the appearances found here on dissection were exactly similar to those observed after both a spontaneous cure and a cure by compression.

The explanation usually given is, that the coagulum extends from the sac into the artery above and below it, which prevents the entrance of blood; this after a time becomes absorbed, the artery at the part gradually contracts, and is eventually converted into a solid cord. But we have seen that the artery remains pervious for some distance between the point at which the ligature is applied and the sac, and that a current of blood probably continues to pass through it after the operation, which would necessarily interfere with the formation of a coagulum in the artery at this part. Others suppose that inflammation sets in here, which unites the opposite sides of the artery; but they do not give any reason why the adhesive inflammation should be so conveniently set up at this particular spot; besides, we know that the vessel is obliterated at the same place when a spontaneous cure occurs, or where this followed the employment of pressure, although no adhesive inflammation occurs in either of the latter cases. The explanation becomes easy, however, if we admit that a current of blood continues to pass through the sac after the operation; the oblitration of the artery will be effected exactly in the same way as occurs in cases of spontaneous cure, or where compression had been employed.

Every thing that has now been said makes it probable that the ligature of the artery at a distance from the sac, and compression of the vessel at the cardiac side, effect the cure of aneurism in the same way. It has already been shown that the mode in which nature brings about a spontaneous cure is precisely similar; which of itself is a strong argument in favour of its correctness. But there is another circumstance which tends still further to confirm it-viz., that several phenomena connected with the surgical treatment of aneurism which were hitherto obscure, and inexplicable upon the theory that the

coagulation of the contents of the sac always follows the operation by ligature, are readily explained according to this theory.

For instance, we have seen that a slight pulsation is not unfrequently felt in the sac subsequent to the operation. Now, this theory not only explains its cause, but it shows why it ceases after a short time, and why, instead of being an unfavourable sign, it should rather be regarded as a favourable one.

By this theory alone, we can account for the artery being obliterated after the ligature at a point from which the aneurism springs, while it remains pervious between the ligature and the sac.

Lastly, it enables us to explain why suppuration of the sac should occur after the operation in one case and not in others apparently similar; and how a secondary aneurism forms in certain cases a long time after the operation, while in general it must be a rare result of the ligature.

Spontaneous cure of external Aneurism.

Every writer upon aneurism mentions or refers to cases where an external aneurism ceased to pulsate some time after admission into hospital, although a bandage had been merely placed round the limb (with or without compress upon the tumour,) but without the slightest intention or expectation of producing any effect upon it. Such cases are comparatively rare, and hitherto have been looked upon as the result of some happy chance which might occur once or twice in a practitioner's life, but from which no deductions could be drawn. "Such instances of inexplicable recovery (a recent writer observes) are extremely rare, and as examples of singular good fortune, are rather to be hoped for than expected; neither can any principle of practice be established on them."

In Mr. Porter's excellent practical treatise on Aneurism, published a few years since, two cases of this kind, which occurred in the Meath Hospital, are shortly reported. "Some years since (he says) a man suffering from aneurism was admitted into the Meath Hospital. The tumour was situated low down in the popliteal space, and was large, being fully the size of a turkey's egg. The limb was semiflexed, and could not be extended; pain very considerable; tumour not compres sible, at least pressure influenced its size but slightly; it was hard, and did not diminish in bulk when the femoral artery was compressed, which, however, stopped the pulsation. With a view to humour the patient, until he could be persuaded to submit to an operation which I conceived to be absolutely necessary, I rolled a large bandage round the entire limb, from the toes upwards. This, as the idea of treating the disease by compression had never been contemplated, was very loose; nor had I the least notion that the tumour could have been influenced by it, one way or another. But on my visit the next day the aneurism was gone. Within an hour after the application of the bandage, the patient experienced some pain in the tumour, which soon became excruciating, and continued during the entire night. In the morning the tumour no longer pulsated-it had become solid and firm, and eventually the disease was cured.”