It is necessary that this enlargement of the collateral branches should lake place at an early period, because in many cases of aneurism the artery beyond or below the tumor is obliterated long before any operation is performed. The main supply of blood has been already cut off from the extremity, and the operation adds very little to the derangement of the circulation which has for some time taken place below the tumor.
When an operation has been successfully performed for aneurism, and the patient has died some time afterward, dissection has shown various arteries enlarged, both above and below the part where the trunk was obliterated by the ligature; and not only an enlargement of arteries, which, from their regularity have received names, but others have been developed not usually known to exist, or not of a size to be conveniently traced. These through their frequent anastomoses bring the blood at last into several large trunks, by which it is again conveyed to the original vessel below all and every obstruction which may have taken place; thus compensating by a circuitous route for the loss of the direct supply. The principal object of inquiry is, do these vessels always exist, or at what period of time do they begin to enlarge, so as to enable them to carry on the circulation, in the manner in which it is presumed to be done?—for few will assert that the enlargement of these particular collateral vessels was an accidental play of nature, and existed previously to the commencement of the disease or injury for which the operation was performed. On this point, the theory of the operation for aneurism and its applicability to wounded arteries appears to hinge; and, what is of more importance, on which the practice resulting from it depends.
Two distinct kinds of collateral circulation are at present acknowledged: one by direct large communicating arteries; the other through the direct medium of the capillary vessels inosculating with each other. Where direct communicating arteries exist, little subsequent change beyond enlargement takes place in them. It is otherwise with the indirect capillary vessels. When the radial or ulnar artery has been divided in the hand, the blood will not only flow readily from each end of the divided vessel, but equally red and arterial from both, the communication being through direct arterial branches from one vessel to the other. It will also be red and arterial if the division take place at the wrist, and may be so in the brachial; but if the femoral in the lower part of the thigh be wounded, the color of the blood issuing from the lower end of the artery, if any issue at all, will be dark or venous. It is so, because it has been obtained from the capillary arteries, which in this case being empty received blood by regurgitation from the veins, the valves of which when present do not prevent its reflux course. If a limb be injected and carefully dissected four or five days after a ligature has been placed during life high up on the principal trunk, the capillary vessels will be seen to be well injected; but few or none will be found large enough to admit of their inosculation being traced throughout. If another limb be injected and dissected, some sixty days after the ligature has been applied, a difference will be distinctly observed between the two preparations. In the latter, the capillaries will not appear to be so fully injected, but several larger and more tortuous vessels will be found in situations where they were not expected to exist; and the anastomoses of these one with another, generally by arches, may be traced to their communication with the principal trunk, both above and below the obliterated part. If an incision were made in the nearest pervious portion of the lower part of an artery in the thigh of a person who had undergone this operation, arterial blood would issue from it. The communication would have become direct by communicating branches, and the capillaries would have returned to their accustomed duties.
178. During the first twenty-four hours after the division of an artery such as the femoral, or the application of a ligature, the temperature of the limb is commonly diminished; after that period, and as the action of increase takes place, the temperature is usually from three to five degrees higher than in the opposite healthy limb. At the end of from eighteen to twenty-eight days, in a successful case, it is found to be equal in both.
It is asserted by some sanguine supporters of the all-powerful influence of the collateral circulation, that it is sufficient at all times, and under all natural circumstances, to maintain the life of the extremity. The practice of the Peninsular war proved the fallacy of this opinion in too many instances to admit of any doubt of its inadequacy to do so in the lower extremity after the division of the femoral artery, under ordinary circumstances. The fact of enlargement or of a new development of vessels having taken place after the commencement of disease or the reception of an injury, has been demonstrated by dissection, and it is through them the life of the limb is to be preserved; but time is required for their development. When a limb is lost through mortification, as the consequence of a division or obstruction of the principal artery, it usually takes place after the infliction of a sudden injury, in consequence of these collateral branches not having had time to enlarge.
179. The collateral circulation is therefore not the same, and is not in the same stage of preparation, in a limb suffering from a divided or wounded artery, as in one in which an aneurism has for some time existed; this is the reason why mortification is more common after wounded arteries than after operations for aneurism.
LECTURE X.
PROPER TREATMENT OF WOUNDED ARTERIES, ETC.
180. The due appreciation of the means adopted by nature and by art for the suppression of hemorrhage, as well as the proper treatment of wounded arteries, is owing to the surgery of the war in the Peninsula. They were suspected after the battles of Roliça, Vimiera, Oporto, and Talavera, but did not receive their complete development until after the battle of Albuhera. It was not until after that of Toulouse they were partially admitted; and it is only of late that they have been almost everywhere acknowledged, taught, and practiced.
Previously to the time of Mr. Hunter, the diseased or dilated state of the coats of an artery which constitutes an aneurism was, when it occurred in the ham, very often fatal. The operation of Anel, first performed in 1710, of cutting down to the artery, and placing a ligature upon it immediately above the dilated part, was not approved, and Mr. Pott, the great contemporary of Mr. Hunter, recommended in bad cases that amputation should be resorted to in the first instance; although Desault had succeeded, in 1783, in a case of popliteal aneurism, in which, after the manner of Anel, he had placed the ligature on the artery a little above the aneurismal swelling in the ham. Mr. Hunter’s contemplative mind, aided by his knowledge of anatomy and of disease, led him to believe that the ligature thus applied on the artery in the ham failed, because the vessel was unsound at that part, and was therefore incapable of taking on those healthy actions necessary for the obliteration of its canal above the ligature, which are known to take place when the artery is in a normal state. He concluded that this was sufficient to account for the failures, without especially taking into consideration the difficulty of applying the ligature in the ham immediately above the aneurismal sac, and of the probability of the sac suppurating when thus molested; an occurrence aiding materially in the necessity for the loss of the limb by amputation, performed then under circumstances of constitutional irritation, which would render it less likely to be attended with success.