The collateral connection of the femoral with the popliteal artery is established through two channels: 1. through the anastomoses between the branches of the profunda, as well the ex ternal circumflex as the perforating arteries, with the branches of the popliteal ; whence the femoral may be interrupted at any part below the origin of the profunda, and the blood thus find a ready passage from it into the popliteal : 2. through those of the branches given by the femoral to the vastus internus and the superficial superior internal articular with the same.
To the channels of communication which have been described are to be added, as pointed out by Scarpa, those established, by the arteries of the periosteum and of the in ternal structure of the femur, between the main arteries above and below. The former are well represented by Scarpa,* and are formed by anastomoses between branches of the external circumflex, the profunda, the femoral and the popliteal distributed to the periosteum.
Upon a review of the anastomotic con nections of the femoral artery, its course pre sents two stations at which communications are established, on the one hand with the main artery above, and on the other with that below, while in the interval they are connected the one with the other. Those are, 1. the first part of the vessel's course from its commence ment to below the origin of the profunda ; and, 2. its lower part for so much of it as includes the origins of the branches to the triceps crural and adductor muscles, and the superficial superior internal articular.
Again, it appears that through the first station, not only is the femoral connected with the arteries of the trunk and with the lower part of the vessel, but also it is connected without the Intermedium of the second with the popliteal artery, the latter forming by much the more free channel of communication be tween the two vessels, whence the circulation of the lower part of the limb may be pre served independent of the communication be tween the upper and lower parts of the femoral artery, as has been exemplified in the case of Sir A. Cooper given in the Medico-Chirur gical Transactions, vol. ii.; and, lastly, a com munication exists by which the blood may be conveyed from the arteries of the trunk into the popliteal artery and the arteries of the leg, independent of the femoral and without trans mission through any part of its canal.
Bence varieties may be expected in the con dition of the femoral artery in cases of inter ruption, according to the situation of the interruption, and the influence of it or other circumstances in determining the course which the circulation is to take.
When the artery is obstructed above the origin of the profunda independent of aneu rism, the origin of that vessel being free from disease, it would appear that the trunk of the femoral does not undergo any alteration in its capacity, at least from the origin of the pro funda downward : when an interval exists between the point of interruption and the origin of that vessel, the trunk may be di minished for so much, while again it may continue unaltered ; thus in Sir A. Cooper's ease already referred to, the vessel was found reduced to about half its natural size between the origins of the epigastric and circumflex ilii arteries and that of the profunda, and from the latter it preserved its ordinary size through the remainder of its course : in Mr. Norman's caset on the other hand, it was of its natural size in the interval adverted to, but inasmuch as the origin of the profunda was obstructed in the latter case, it cannot be considered so fair an instance of the influence of the simple interruption at the part specified as the former, in which the femoral artery remained pervious after the cure of the aneurism. It is hence to be inferred, 1. that interruption of the femoral above the origin of the profunda or of the external iliac artery is not necessarily followed by obliteration of the former, unless it be of so much of the femoral as might intervene between the interruption and the origin of the profunda, where the ligature has been applied to the former: 2. that in such case the internal iliac is thenceforward the principal source from which the supply of blood to the lower extremity is to be derived; and that the profunda artery through its inosculations with the branches of the internal iliac, constitutes the chief channel through which the transmission of the blood to the trunk of the femoral and the limb takes place: 3. that the external iliac artery con tributes, but in an inferior degree, to the sup ply of the limb, when the interruption is in the femoral itself: 4. that the femoral artery and its branches thenceforward are to be con sidered branches of the iliac arteries, rather of the internal than of the external, the trunk of the femoral itself being secondary to its own branches, by which the blood is transmitted into it from the iliacs.