c. The third, the circumflex branch, pursues at first the course of the original vessel, and runs outward across the upper extremity of the shaft of the femur below the great troehanter, beneath the realm and tensor vagina muscles, and superficial to the crurwus. It gives, in this situation, branches to the crurwus, the iliacus, the rectus and tensor muscles. It then passes backward upon the outside of the femur to its posterior part, and thus surrounds the hone upon its anterior and external sides. In the latter part of its course it traverses the upper extremity of the vastus externus, and gives off, I. branches upward and downward into the muscle; 2. a branch or branches which run between the vastus and the bone, and supply the periosteum ; 3. a branch to the glutceus maximus at its insertion, which, after furnishing it branches, perforates the muscle and becomes superficial. The circumflex divi sion of the external circumflex anastomoses with the internal circumflex, the glutmal, the sciatic, and the perforating arteries. The ex ternal circumflex artery is accompanied by a large vein, which crosses between the femoral and profunda arteries, superficial to the latter, in order to join the femoral or the profunda vein.
2. The internal circumflex artery is a larger vessel than the external : it is given off by the profunda usually after the external, and arises from the inner side of the artery, but at times it arises before the external. According to Harrison it" very frequently proceeds from the femoral artery, prior to the origin of the pro funda;" it has been found by Burns• arising from the external iliac artery, and also from the femoral artery a little below the crural arch. In the former case " it ran along the front of the lymphatic sheath ;" and in the second " it traversed the front of the common sheath of the great vein and also of the lymphatics ;" and in either case, as observed by Burns, it must be exposed to great danger in operation for femoral hernia. According to Green,* both circumflex arteries sometimes are furnished from a common trunk. it runs inward, back ward, and downward toward the lesser tro chanter into the deepest part of the inguinal region, and escapes from that space posteriorly between the tendon of the psoas and the pecti nails muscles ; continues its course backward, on the inside of the neck of the femur and the capsular ligament, below the obturator exter nus, behind the pectinalis, and anterior to the adductor magnus and the quadratus muscles, until it has got behind the neck of the bone; and lastly, it passes through the internal, which separates the inferior margin of the quadratus femoris from the upper margin of the adductor magnus, and thus gains the posterior region of the thigh, where it terminates as will be de scribed.
The internal circumflex artery is the vessel which gains the deepest situation in the groin: it is internal and posterior to the profunda, and when it arises from that artery, while external to the femoral, it crosses the latter vessel poste riorly in its course. While within the inguinal region the internal circumflex artery gives off first a branch to the iliacus and psoas muscles: then a considerable branch, denominated by Tiedemann superficial circumflex branch, which contributes to supply the pectinalis, the adduc tor longus, and the adductor brevis : it runs upward and inward upon the pectinalis, at the same time giving branches to it and to the ad ductor longus, until it reaches the interval be tween these muscles : it then divides into two, of which one ascends in the course of the original branch, between the muscles men tioned, toward the origin of the adduetorlongus, supplying the two muscles, and ultimately anastomosing with branches of the obturator artery : small branches of it traverse the adduc tor, and become cutaneous upon the upper and inner part of the thigh. The second branch
passes downward and backward, also between the peetinalis and the adductor longus, gains the anterior surface of the adductor brevis, and there meets the obturator vessels and nerves: it. divides into several branches, of which some are distributed to the last muscle, some anas tomose with the obturator artery, and others with the upper perforating artery.
Behind the pectinalis the internal circumflex artery gives several branches. Downward it gives a considerable one to the adductor mag nus, which descends into that muscle, supplies it and anastomoses with the perforating arteries. Upward and forward it gives to the adductor brevis and the obturator externus branches which communicate freely with the obturator artery after its escape from the pelvis. Out ward it gives the articular artery of the hip a branch, small, but remarkable for its course and destination ; it enters the articulation beneath the transverse ligament, through the notch at the internal and inferior part of the margin of the acetabulum, over which the ligament is thrown; supplies the adipose structure which occupies the bottom of the socket, and is con ducted by the ligamentum teres to the head of the femur, in which it is ultimately distributed. That part of the artery which reaches the head of, the femur is of very inconsiderable size, and is the source upon which the nutrition of that part depends in fracture of the neck of the bone within the capsule. Lastly, upward and back ward the artery sends off a considerable and regular branch which is usually described as one of its terminating branches, but which, in the opinion of the author, may with more pro priety be considered as belonging to its middle stage. It passes upward and outward between the obturator externus and the quadratus mus cles to the trochanteric fossa, where it is dis tributed to the muscles inserted behind the trochanter, viz. to those which have been just mentioned; to the obturator internus, the gemelli, the pyriformis, the glutcei medius and minimus, and to the back of the ilio-femoral articulation, and where it inosculates with the glutceal, sciatic, and external circumflex arte ries. It may be appropriately called the poste rior trochanteric* branch.