When true aneurism occurs in the poples, there is at first a small colourless tumour pulsating strongly, and containing only fluid blood; occasion ing little or no pain, merely some irregularity of the circulation in the limb, with a spasmodic af fection of the muscles, which recurs during the night and prevents sleep. On pressing the artery nearer the heart than the tumour, it is easily emp tied and divested of pulsation; and on removing the pressure, the aneurismal sac is immediately filled, and the pulsation returns. Gradually as the dilates its powers of resistance are diminished, and the interior of the sac becomes coated with coagu lated blood, which is deposited in layers or strata that thicken its walls, and render the pulsation more and more languid, and also prevent the sac from being completely emptied. Acute pain is felt in the limb, particularly below or distad to the tumour, in consequence of the pressure of the co agulated blood on the nerves, and the motion of the fluid in the sac has been compared by the patient to boiling lead. When the cellular tunic of the ar tery ruptures from over distension, it is converted from the true to the circumscribed false aneurism. The tumour feels now nearly solid, there being a faint pulsation opposite the aperture of the vessel. which however may point centrad, and then none is felt. When the cellular cyst forming the limits of this tumour of almost coagulated blood also rup tures, the blood escapes into the surrounding cel lular tissue, diffusing itself in all directions, and forms an irregular shaped tumour, without the least pulsation, and sometimes nodulated. The pressure of the blood benumbs the nerves, impedes both the arterial and venous circulation, particularly the latter, together with that of the lymphatics, the limb consequently feels benumbed and cold, becomes oedematous, swollen, and of a leaden colour, and the joint is imneded in its motions. One or more projecting points of the tumour pro gressively become thinner from absorption by the pressure of the blood, or the integuments slough and ulcerate, until at last the blood hisses out, and the patient becomes exhausted from repeated he morrhages, but never dies instantaneously. The same process takes place when aneurism occurs in the contiguity of the trachea, oesophagus, stomach, and other mucous structures: but when a serous membrane, as the pleura, forms the wall of an aneurism, it is lacerated. When a bone is pressed upon, it becomes carious. It occasionally happens that the sac increases in the direction of the artery, and presses on it beyond or distad to the tumour, and obliterates its cavity; the sac at the same time becoming entirely filled with depositions of fibrin, which extend into the artery at both ends to the nearest large branches. At other times, the tumour compresses the artery above or proximad to itself, producing adhesion of its coats with obliteration of its cavity; in other instances, this proximal portion of the vessel is plugged up with a dense compact bloody coagulum. In these cases, according to the blood effused, does absorption take place, or in flammation, suppuration and ulceration, or inflam mation and gangrene; and if the patient has strength to support these events, he is cured of the aneurism, the cure being termed spontaneous.
In this gradual development of an aneurism, the trunk of the artery becomes diminished in calibre, and the flow of the blood is also rendered tardy by passing out of its course, by which means the blood is forced into the neighbouring small anastomosing branches that become enlarged. This results particularly if the artery is plugged up. In some cases, the lateral and central walls of the sac are strong enough to resist the pressure of the blood, while the integuments are too feeble, the lat ter therefore undergo the changes just described in the circumscribed false aneurism. Some cases of
aneurism are exceedingly difficult in their diag nosis, particularly the subclavian and carotid.
The treatment of aneurism consists in general and local remedies, the former being chiefly appli cable to internal aneurisms, or those situated with in the cavities, the latter to external ones, or those of the extremities, neck, and external aspect of the head. The general remedies are, abstracting blood in small quantities, confining the patient to bed, and keeping him on low diet, the application of a firm compress to the tumour, with a bandage rolled from the toes equally upwards to the groin. This is al so named the palliative, or Valsalva's treatment, from his being the inventor, in whose hands, as al so those of others, it has succeeded. Cold astrin gent applications, especially ice, have been also re commended. But in aneurism of the extremities there are many cogent objections to this. In the first place, the patient may be so reduced by the confinement, as to be unable to withstand the sub sequent confinement after the operation, since, in many cases, it is necessary to remain quiescent in bed for three or four months, for fear of secondary hemorrhage. In the next place, if much blood be effused, the absorbents are incapable of removing it, and inflammation, suppuration, and ulceration, or gangrene takes place, producing great reduction of strength. Thirdly, occasionally great pain is produced by the pressure. This plan therefore can only be judiciously pursued at the very com mencement of external aneurism. The reader is referred to the essays and works of Senfio, Freer, Dubois, Sir William Blizard, Deschamps, Scarpa, Seiler, Percy, Duret, Assilini, and Crampton, for various modes of compression.
Formerly when this plan of Valsalva failed, am putation was performed, which however is now limited to those cases of diffused aneurism where it appears the absorbents cannot possibly remove the effused blood, and where extensive suppuration and ulceration of gangrene must be the result. About fifty or sixty years ago, the surgeons of Italy, em boldened by Haller's doctrine, drew a ligature around the popliteal artery both above and below the sac, which they laid open and removed the coagula. This extensive wound healed by granu lations, or produced sinuses and caries of the bones, with contraction of the joint. Secondary hemorr hage from securing a diseased artery was also a frequent occurrence; and yet this practice is still followed by Boyer and many of the French sur geons. The celebrated John Hunter, perceiving such unhappy results, performed several experi ments on the lower animals, and proved that an artery close to an aneurismal sac is so diseased that it must ulcerate; whereas, if secured between the tumour and the nearest large branch, so as to have the vessel healthy on the one side, and remote enough on the other from the branch, so that the latter would carry the blood along it on the princi ple of hydraulics, and leave the tied portion at rest, that a coagulum of blood might take place, and the adhesive inflammation not be disturbed, the opera tion would succeed in the majority of instances. He also saw, that if this operation was performed early enough, the flow of blood into the aneurismal sac would be so far checked as to allow further co agulation of it, and that ultimately both the blood and cyst would be absorbed. Accordingly, in 1785 he secured the superficial femoral artery for popliteal aneurism, shortly after its giving origin to the profunda, but he improperly employed four ligatures, whereas one is now found sufficient, for which important improvement we are indebted to Freer. This operation has undergone many im portant improvements by Birch, Foster, Freer, Abernethy, Dionis, Richter, Jones, A. Cooper, Travers, Hutchinson, Roberts, Lawrence, Hodg son, and Dalrymple.