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During violent and sudden exertions the more brittle parts may burst, either at a certain point, or throughout the whole circumference of the artery; and on this such results will supervene as on ulceration of the internal tunic. Ecchymosis then takes place under the cellular coat, which becomes thickened, and incorporated with, and strengthened by, the surrounding tissues; this is the incipient state of an aneurismal tumour. The effusion of blood, gradually increasing, distends the cellular coat, forming the cavity into which it is poured, and produces a tumour of a size proportional to the distensibility of the tunic and the force of the effusion. Sometimes the external coat is separated from the others to a considerable extent by the insinuation of blood. An aneurism, however, may exist from simple dilatation of a portion of the vessel, gradually increasing, and forming a cavity in which the blood accumulates. At one time it was supposed that all spontaneous aneurisms were caused by simple dilatation of the canal; but such an opinion has been long shown to be incorrect, and the term of true aneurism is now confined by many to that tumour and accumulation of blood consequent on the giving way of the internal coat, and situated externally to the canal of the artery. It is true that dilatation may occur previously to the giving way of the coats, and thus the two causes are combined. The dilatation occurs from the calibre of the artery being considerably diminished, in the first instance, at the point where its coats have undergone the calcareous degeneration, and only acts as a predisposing cause to the failure of the coats when thus diseased. When there is mere dilatation, the tumour is generally of an oval form; but when the internal coat gives way, a lateral prominence is formed, and gradually increases in size. The shape of the true aneurism is various: sometimes the tumour is globular, with a narrow neck; and, from this being of considerable length, it becomes difficult, in some situations, as above the clavicle, to ascertain the particular artery which is the seat of disease, the globular extremity of the tumour presenting itself at some distance from the vessel with which its pedicle is connected. This is rare, however. At other times its form is very irregular, being most prominent at the part where the accumulation of the blood is least resisted. Pulsation in the tumour is distinct from the first, and is painful to the patient; and in the external aneurisms it is so strong as to be perceived by a bystander at a considerable distance. The tumour is at first compressible, and completely disappears on firm pressure being applied, either directly to the sac, or to the artery above, the sac being thereby emptied of its contents, or prevented from being filled. It may sometimes be difficult to form an accurate diagnosis, from the circumstance that tumours, not aneurismal, receive a pulsatory movement from an artery or from arteries immediately beneath them; such difficulty is obviated by attention to this simple test—that in an aneurism the pulsation is felt equally in all directions. Besides, if the tumour is moveable, it can be partially displaced, so as not to lie immediately over a large artery, and, if it be not aneurismal, it will then be found to possess no pulsation; if it be an aneurism, its pulsation will not be diminished by any change of position.

The blood contained within the aneurismal sac, being comparatively motionless, coagulates, and the coagulum is attached to the inner surface; at first it contains red globules, but it afterwards loses them, and becomes of a pale hue, consisting solely of fibrin. This coating gradually increases, and attains no small thickness, fresh portions of fibrin being superadded in concentric laminæ. These layers are chiefly deposited from the blood within the cavity, but they also appear to receive addition from lymph being effused by the vessels proper to the original parietes of the tumour. By such thickening, it can be easily conceived that the pulsation will be somewhat lessened. In large aneurisms the accumulation and deposit of fibrin may be much greater at some points than at others, and hence pulsation may be rendered “not equal in all directions.” It is not, however, diminished to any great extent; for absorption of one or more points occurs, and the coating is again attenuated.

In some rare cases the deposition of fibrin has gone on gradually accumulating, filled completely the aneurismal cavity, and thus effected a spontaneous cure, the remaining solid tumour imperceptibly diminishing by the action of the absorbents. After obliteration of the aneurismal cavity, the fibrin is generally deposited in so great quantity as to occupy the calibre of the vessel above and below the tumour, obstructing the progress of the blood, causing it to flow by the smaller and collateral branches, and effecting a spontaneous cure, somewhat similar to that produced by the artificial application of a ligature. Coagula are seldom formed in the dilated vessel, to whatever size it may be enlarged, unless there is fissure of the internal coat; for in no other way can a portion of the blood readily become stagnant, while the calibre of the vessel remains pervious. There is in my collection a preparation of dilated aorta, to the coats of which adheres a large firm coagulum. Occasionally, though rarely, a dilatation of the internal coats is met with accompanied by thinning of the external ones. Of this sort of diverticulum, there is also a good specimen in the collection here alluded to.

A spontaneous cure may also be accomplished from the original aneurism being compressed by one of a more recent origin, causing ultimate obliteration of the canal. Of this I recollect one remarkable instance; the patient was afflicted with an aneurism of the axillary artery, which had attained a large size, and the cure for the disease in this situation being then unknown or unattempted, the patient was considered as lost; but some time after the tumour began to diminish, and disappeared. The patient died; and the cause of death was found to be the giving way of an aneurismal tumour of the arteria anonyma, which was situated so closely to the aneurism of the subclavian as to have acted as a mechanical compress, causing obliteration of the vessel at that point.

When a cure has been effected, the vessel is found to be converted into a dense and impervious cord at the site of the tumour. The canal above is dilated; the coats are thickened, especially the middle; and from the thickening and increased action of the fibres, the internal coat becomes somewhat rugous, the rugæ being in a transverse direction.

The aneurismal tumour in general increases, and approaches the surface, involving and destroying all the intervening textures. If resisted in its enlargement by bone, even this is not sufficient to impede its progress; the bone is absorbed, and perhaps ulcerated, at the point where it is compressed by the tumour. The osseous is more liable to destruction from this cause than the cartilaginous tissue, contrary to what occurs from compression by abscess. Ultimately the sac gives way, and its contents are discharged either externally, or into an internal cavity or canal, in consequence of its parietes sloughing from the compression made by the tumour; and such termination is instantly fatal.

An aneurism of the descending aorta, in a great measure one from dilatation, is here represented: the patient also laboured under popliteal aneurism of one limb, and inguinal of the other. He died suddenly, in consequence of the giving way of the internal tumour. The escape of blood into the cellular tissue may even take place to such an extent as to prove fatal in a few hours. The disease may also prove fatal by mere compression, as of the trachea, impeding breathing, and inducing disease of the respiratory organs; or by pressure on the gullet preventing the passage of food: in the latter case, however, the dissolution is generally more sudden, in consequence of the compressing part of the tumour giving way, and the contents being evacuated into the stomach or mouth. If the aneurism compress a plexus of nerves, or the spinal chord itself, the anterior part of the vertebræ having been previously absorbed, paralysis is produced.

In consequence of aneurism, the circulation of blood in the vessel is obstructed; hence the collateral branches above the tumour become enlarged, and through them the circulation is continued; by their anastomosis with collateral branches which arise below the seat of the tumour, a portion of the fluid is brought back into the canal of the original artery. The circumstance of collateral enlargement used to be distinctly enough demonstrated in amputation, one of the old cures for the disease.

The tumour may be suddenly increased by a portion of the parietes giving way, and the blood being propelled into the cellular tissue, which becomes thereby condensed, and supplies the deficiency in the original sac; diffuse is thus superadded to the true or encysted aneurism.

The disease is generally accompanied with great pain, the neighbouring nerves being much stretched by the enlargement of the tumour, as in the axilla or ham; in these situations also the limb below the aneurism is much swollen from the compression of the absorbents and veins and consequent infiltration into the cellular tissue. Diffused aneurism from wounds, and the other species of the disease, will be afterwards treated of.

The peculiar degeneration of the coats of the vessels has been already stated to be the predisposing cause of aneurism; and the disease may be directly caused by over-excitement of the circulation, or by an over-exertion of the muscles. It is more frequent in males than females.14 In men somewhat advanced in life the arteries get hard and rigid, whilst at the same time the muscles are strong, the general health good, and the whole frame stout and active; so that the patient is capable of violent muscular action, such as the arteries are ill able to bear, and consequently the internal coat of a vessel yields, and lays the foundation for an aneurism.15 The lower limbs being chiefly subject to such exertions, aneurism in them is most frequent;16 and for the same reason it is said to be common in those who ride much on horseback. Degeneration of the coats of the vessels in the superior extremity is extremely rare. This is another reason why spontaneous aneurism seldom assails them.

Treatment.—In internal aneurism the only indication which can be followed, with any chance of success, is to favour the occurrence of a spontaneous cure, by abstracting all stimuli, mental and corporeal, by enjoining complete rest, by keeping the patient on low diet, and by repeated bleeding. Thus the force of the circulation is diminished, and coagulation, it is said, promoted; by this practice aneurisms, the progress of which defies external means, are occasionally, though very rarely, cured. Ice and other cold applications to external aneurisms, or those which have made their way to the surface, have been recommended to induce coagulation, but their use is not unattended with danger; for they may, in some stages, so far diminish the vitality of the coverings as to cause sloughing, and fatal hemorrhage.

In the treatment of aneurisms exterior to the great cavities, important improvements have been made in modern times. No success can be expected to follow palliative and temporizing measures, and a cure can result only from operation. Formerly it was the practice to lay open the aneurismal tumour, to search for the extremities of the artery opening into the cavity, and to secure them by a ligature, or close them by pressure, styptics, or both. In some few instances this method had permanent success; but in the majority the operation proved wholly abortive, and not unfrequently fatal. It was necessarily tedious in its performance, and attended with much danger, the blood being discharged in great profusion immediately after the opening of the sac, and the extremities of the vessels being with great difficulty detected and secured. Besides, the vessels in the immediate neighbourhood of the tumour having generally undergone the degeneration already mentioned, were incapable of taking on any healthy action; the application of ligature on a vessel thus circumstanced could consequently be productive of no advantage. From this method having almost invariably proved unsuccessful, practitioners in those days generally preferred amputation, when the tumour was so situated as to allow it; and when the disease occupied a situation in the limb so high as to prevent amputation, the case was deemed incurable, and the patient abandoned to his fate. But amputation was accompanied with circumstances almost equally alarming with those attendant on division of the sac: the hemorrhage was very great; for as a consequence of obstruction to the free passage of the blood in the aneurismal vessel, the circulation was chiefly carried on by the collateral anastomosing branches, which were thereby so much enlarged, as, on their division, to pour out blood with a profusion resembling that of arteries of the second or third magnitude. Continued pressure was employed as a less hazardous method of cure, but was equally inefficacious; and was also attended with danger, from the risk of sloughing. If the practice ever proved successful, it was only after a tedious perseverance in its use, and long confinement of the patient.

The operation of applying a ligature on the vessel at a distance from the tumour, and thus intercepting or weakening the flow of blood into the cavity, so as to allow complete coagulation to take place, is of comparatively modern invention, and is the one now practised with almost invariable success. To John Hunter without doubt belongs the merit of proposing and putting it in practice; it has been claimed also for the celebrated Desault. This operation has been variously modified. Some have advocated the temporary application of a ligature, conceiving that the effects produced will be as complete and permanent when it has been allowed to remain only for a certain time, as when it is left undisturbed and ultimately separated by nature. Such a theory, however, has proved to be incorrect in most of the instances in which it has been reduced to practice on the human subject; and the operation is at best very uncertain, and not to be relied on. Others have employed a double ligature, and some of the Continental surgeons have applied a great many; some were tightened, others left loose, and looked upon as ligatures of reserve to be tightened, should hemorrhage take place, an occurrence likely enough to follow their clumsy and unsurgical proceedings. A thick broad ligature like tape has also been used, from an ill-grounded apprehension that all the coats of the artery would be cut completely through by the tight application of a thin and firm one. With the same view, a roll of linen or plaster has been interposed betwixt the noose and the vessel, and this practice has been advocated even by good surgeons—as Scarpa. Such complications can do no good, and may do much mischief. The artery must be greatly detached from its surrounding connections before the numerous and flat ligatures can be applied, in consequence of which its coats will be apt to slough or ulcerate, and hemorrhage occur. When, from any cause, the vessel has been detached to a greater extent than is sufficient for the passing of one ligature, two ought undoubtedly to be used, and one applied close to each extremity where it is attached to the surrounding parts.

Again, it has been proposed, after the application of a double ligature, that the vessel should be cut through betwixt the two deligated points; it being supposed that in this way the closure of each extremity will be more rapid, the cut ends retracting, and being, in fact, in the same circumstances as the extremities of arteries which have been tied on the face of a stump. Mechanical contrivances have also been invented for the compression of the artery,—such as the serrenœud and presse artere; these, however, are clumsy, insufficient, and often injurious.

The single ligature, when properly applied, is the most safe, and preferable to any other, for arresting permanently the flow of blood in a vessel. In its application, the artery must not be separated from its connexions farther than is barely sufficient for the passage of the armed needle beneath it; but the external incision ought to be free, in order that this may be readily effected, and that the operation may be easily and speedily performed. By the firm application of a single ligature, the vessel is rendered impervious; the internal and middle coats are divided, so that the ligature only encircles the outer or cellular one, which resists the influence of any moderate degree of force by which it may be tightened. The blood coagulates above the deligated point,—the coagulum is of greater or less extent, in proportion to the vicinity of a collateral branch, and is of a conical form, the apex of the cone pointing to the free portion of vessel. Incited action in the vessel takes place at the deligated point; the divided margins of the internal and middle coats secrete lymph, by which they adhere, and so obliterate the canal of the artery. Lymph is also effused on the external surface, and in this deposit the ligature becomes imbedded. The direct influx of blood into the aneurismal sac is thus intercepted, and time is allowed for coagulation of the blood which it contains; the artery for a considerable distance below the ligature becomes ultimately converted into a firm and impervious chord. The coats of the vessel above the ligature are much thickened, and the internal membrane is occupied with the transverse rugæ occasioned by projecting fasciculi of the fibres, which are always apparent after obstruction of an artery. If this operation be properly conducted, success must almost uniformly follow. Before determining on its performance, however, the state of the arterial system ought to be examined as carefully as possible; for not unfrequently the degeneration of the coats is almost universal, and therefore an artery, or even arteries, may be diseased at more points than one; and if this aneurismal diathesis exist, the patient may be found to labour under an internal aneurism of the aorta. In such a case, an operation could not with propriety be undertaken for the cure of the external aneurism; there might be no inconsiderable danger of the patient’s death being suddenly accelerated by the operation, the sac of the internal aneurism giving way perhaps during its performance: such a circumstance has actually occurred.

Ligatures composed of animal substance, such as catgut, have been proposed as preferable to all others, on the supposition that they would be absorbed, and occasion less irritation; the fallacy of any such theory has already been adverted to. After the ligature has been applied for some time, it induces ulceration of the external coat which it envelopes, by which means it becomes detached from the vessel; acting as a foreign body, and causing a slight degree of suppuration, it makes its way by nature to the surface and is discharged. The period at which it separates may be said to be from the tenth to the twentieth day; sometimes sooner, seldom later. If, however, much of the surrounding parts have been extensively included along with the vessel, a longer period will probably elapse before the separation of the ligature. One end only of the ligature should be cut away close to the artery, the other being left hanging from the external wound; perhaps it is even safer to leave both, unless a third knot is made upon it; thus the extraneous body, when detached, can be gently pulled at so as to hasten the separation: this must be done with very great caution. When both ends are cut short, and the knot closed in, there is a risk of secondary hemorrhage, from the ligature causing formation of matter round it, perhaps detaching the vessel from its connections, and causing ulceration of its coats.

The operation ought to be performed at as early a period of the disease as possible. Some recommend that it should be delayed in recent cases, with the view of allowing sufficient time for the anastomosing vessels to enlarge, in order that the circulation may be more vigorous in the smaller branches after obstruction of the principal vessel. Such delay prolongs the patient’s sufferings, which are in many cases extremely acute, and the precaution is altogether unnecessary, as has been amply proved by experience. On the same principle, the previous application of pressure to the vessel has been recommended; but few surgeons, if any, are now afraid of trusting to the resources of Nature when the principal vessel of a limb is obliterated, and that suddenly, without previous dilatation of the anastomoses. Cases are on record, in which the abdominal aorta has been completely obstructed by a natural process, without much impeding the inferior circulation; and in one remarkable instance of this description, the inconvenience was so slight that the disease was not suspected during the life of the patient, the lower limbs retaining their usual size and activity. In plethoric habits it may sometimes be prudent to abstract blood, even more than once, previously to the operation.

When the ligature is placed immediately below a collateral branch of considerable size, a bloody coagulum is not formed, though adhesion may occur; but if the excited action should extend to the collateral branch, and its canal become thereby obliterated, a coagulum is speedily deposited. In consequence of the enlargement of the anastomosing branches, and the increasing circulation in them, pulsation generally returns in the tumour, to a slight degree, some days after the operation. This, however, is by no means a sign that the operation has been ineffectual; for the renewed pulsation almost always disappears in the course of a very short time. In one instance only have I found it assume a more permanent and troublesome aspect; in that case, it recurred about ten months after the performance of the operation, but speedily disappeared under the careful use of a compress and bandage.

On account of the aneurismal diathesis, it occasionally happens, that after the cure of one aneurism, another appears in a different situation; in two instances, I operated on both thighs, at a considerable interval, successively and successfully, for popliteal aneurism, in the same patients.17

When the tumour is so situated as not to admit of the application of a ligature between it and the heart, it has been proposed to place the ligature on the distal side of the aneurism, upon the supposition that coagulation will occur within the sac in this case as after the common operation.18 The practice has been made trial of, but its expediency appears very doubtful; neither has the success attendant upon it been such as is generally supposed: the post mortem examinations have been very unsatisfactory in some of the cases. The application, indeed, of a ligature in that situation can seldom be of any advantage, the artery being already obliterated, in aneurisms of some standing, a long way beneath the tumour; and it is, perhaps, from this circumstance that, in such operations, great difficulty has been experienced in securing the vessel, and that it has been thought necessary even to pass a needle under a thick mass, somewhat in the situation of the artery. It would appear, in some instances, that the artery when pervious had even remained untouched, not being even exposed by the burrowing process employed by some of the operators; and that if any vessel was tied, it was not the trunk in which the disease existed. It would appear that a very correct diagnosis had not been formed in some of the cases.

The appearance of the vessel after the application of a ligature above the tumour has been already shown. The obliteration of the sac proceeds, in some cases, very rapidly; it assumes a harder feel, decreases, and disappears; being connected with the vessel by means of a dense impervious chord, to which condition that portion of the artery has been reduced. The anastomosing vessels enlarge more and more, carry blood freely from above to below the ligature, and thence to below the tumour; some even passing to the latter situation directly from above the ligature. Along with the muscular and other branches, the neurilemmal vessels also become enlarged, and compress the nervous filaments; and to this are to be attributed the annoying pains which sometimes occur in a limb after the operation for aneurism. The enlargement of the arteries of the neurilemma can be distinctly shown by dissection.

Immediately after the operation, the circulation in the limb cannot be so vigorous as before; its temperature is consequently diminished, and it possesses less power of resisting the influence of stimuli. The limb ought to be kept only moderately warm; for if too much heat be applied, there is a risk of gangrene. The temperature afterwards rises, and soon gets above the natural standard; the blood, from obstruction in the internal parts, being chiefly determined to the surface. After the collateral circulation has been completely established, the limb regains its natural temperature.

Secondary hemorrhage is occasionally a consequence of this operation; nor is it to be wondered at, should one ligature only be used, seeing that this is often clumsily applied; the cellular tissue being lacerated, and the vessel detached from its connections by the use of blunt instruments, directors, and silver knives. When many ligatures are employed and foreign substances placed in the wound, the patient can scarcely be expected to escape profuse bleeding. If, however, the operation by single ligature be properly performed, and the coats of the artery be sound at the deligated point, the occurrence of secondary hemorrhage must be rare. It generally supervenes when the ligature is about to separate: at first there is a thin bloody discharge, afterwards the quantity of blood is more copious; it is evacuated at first in a gentle and continued stream, but afterwards per saltum, and in profusion. The discharge not unfrequently stops for a short time, but, on the circulation being excited, it again returns; and the patient soon dies, unless active measures be practicable, and immediately resorted to. Compression can be of no use; nor can astringents, nor venesection, which I have actually seen practised in such cases. The application of a ligature betwixt the heart and the open point of the vessel affords the only chance of saving the patient; the surgeon must interfere, and do what is in his power—he cannot look on and see the patient bleed to death.