The continuation of the nerve, or what may be termed the posterior trunk, inclines slightly backwards from between the tendon of the sartorius and gracilis, and on a level with the knee-joint is a little to the inner and back part of the tendon of the latter. Having received its connection with the cu taneous branch of the obturator, it passes in company with the saphmna vein into the re gion of the leg, inclining slightly forwards to the back part of the inner border of the tibia. Having supplied the integuments at the upper, inner, and anterior part of the leg, it inclines slightly backwards about its middle, sends filaments to communicate with the continu ation of the cutaneous branch of the obturator at the posterior part of the leg. It then again inclines forwards, and terminates about three or four inches above the ankle in two branches. The anterior terminal, the smaller of the two, supplies the skin at the lower sixth of the inner and front part of the leg, and over the front of the ankle joint, a few of the branches entering the articu lation. The posterior terminal, apparently the continuation of the trunk, supply the inte guments over the inner malleolus, upper, inner, and back part of the foot.
The saphaenus nerve not unfrequently, in its course in the thigh, in company with the fe moral artery, gives off, at a variable height, usually however at the lower fourth of the leg, a small branch corresponding more or less with the distribution of the outer division of the accessory sapbmnus. The internal sa phmnus nerve first lies behind the correspond Mr' vein; then in front of it to the middle third oftsthe leg, when it again is placed behind it : an inch or two before it divides into its ter minal branches, it is again anterior to it, the latter passing over in front, and the other behind.
The obtztrator nerve, derived from the third and fourth, and sometimes also from their internal intercommunicating branch, is much smaller than the anterior crural, and rounded. It perforates the inner border of the psoas, along which it is conducted to the pelvis, a little below the level of which it runs to between the external and internal iliac ves sels. It then passes obliquely behind the ex ternal iliac vein, crossino. it at a very acute angle, and reaches the aturator foramen in company with, and above, the obturator artery. It passes through this foramen into the thigh, and terminates by dividing into super ficial and deep divergent muscular branches, situated behind the pectinmus and adductor longus. Soon after its origin a small nerve, the accessory obturator, is occasionally ob served to proceed from the outer part of the trunk. It passes in company with the femo ral vein, anterior and internal to it, beneath the femoral arch, over the horizontal ramus cf the pubis, and external to the pectinmus.
It is then directed a little inwards, and divides into several branches, some of which .enter the joint through the anterior part of the cap sular ligament ; others supply the posterior surface of the pectinwus, and the remainder, as the continuation of the nerve, terminate by communicating either with the upper part of the trunk of the obdurator itself, or with the branch of the nerve destined for the adductor longus.
The obturator nerve, in passing through the subpubic canal, gives off two or three branches to the obturator externus muscle : one pene trating its upper edge, the others its anterior surface. Some articular filaments are also sent off in this direction, and accompany some of the branches of the inferior division of the obturator artery, beneath the trans verse ligament to the hip-joint. The relation of these filaments as to size and numbers, how ever, is not constant, being in the inverse pro portion to the size and number of branches given off from the accessory obturator, which is not unfrequently absent.
From the superficial branch is given off' a long filament internally to the gracilis muscle, which runs for about tun o inches along the outer surface of the muscle before entering it, another to the posterior surface of the pec tinfcus, which varics in its size according to whether this muscle be supplied by the ac cessory obturator or not : and a third to the adductor longus, which also enters its posterior surface.
The most important branch, however, is the long cutaneous branch which emerges from behind the lower border of the adductor lon gus muscle, passes in the fascia behind the internal saphaena vein as far as the knee joint, where it perforates the fascia, and becomes cutaneous at the anterior border of the tendon of the gracilis muscle. In this part of its course, a little below the upper third of the thigh, it communicates either with the internal branch of the accessory sapluenus, or with a branch occasionally given off from the saphx nus itself, and which accompanies the saphwna vein to the knee joint. It gives off cutaneous branches to the middle of the thigh, forming, with the above nerve, a more or less intricate plexus. Having perforated the fascia on a level with the knee joint, above it, or a little below it, it communicates with the trunk of the internal saphxnus (being occasionally only in apposition with it), and internal cuta neous nerve. It terminates by being directed downwards and backwards to above the lower part of the poplitasl region, and continues to give off cutaneous branches, till it is lost in the integument at the inner and back part of the leg to within two or three inches of the ankle : having previously sent filaments of communication to the continuation of the saphxnus nerve.