Third, the _femoral artery_, which passes beside the vena cruralis and extends down the posterior surface of the thigh to the knee-joint, supplies the upper thigh muscles with the exception of the adductor muscles. [Illustration: FIG. 66.—Blood-vessels and nerves of the posterior extremity. Outside view. 1, Anterior tibial artery. 2, Metatarsal artery. 3, Digital arteries. 4, Vena cutaneous crurus. 5, Ischiadic artery. 6, Vena cruralis. 7, Lateral cutaneous branch of the ischiadic nerve. ] [Illustration: FIG. 67.—Blood-vessels and nerves of the fore limb. Outside view. 1, Median nerve. 3, Ulnar nerve. 4, Radial artery. 5, Recurrent ulnaris artery. 6, Twigs of ulnar artery to wing feathers. ] The =ischiadic artery= (Fig. 69, No. 9) forms the main artery of the posterior extremity. This artery, the largest vessel of that region, is given off from the posterior aorta and passes ventrally over and between two of the main lobes of the kidney. The continuation of the posterior aorta is called the _sacralis media_ (Fig. 64, No. 32). The ischiadic artery gives off a _recurrent renalis_ on the posterior lobe of the kidney (Fig. 64, No. 33). On the left side it gives off a branch to the oviduct and to the ligament of the oviduct. The main trunk leaves the cavity with the ischiadic nerve (Fig. 65, No. 1) through a foramen formed by the os ilium and the os ischium. It sends branches into the adductor muscles of the upper and the lower thigh. It gives off anastomotic branches which unite with those from the femoral artery. At the flexure of the knee-joint it gives off two branches to that region (Fig. 69, No. 10). It gives off another branch to the gastrocnemius muscle and one to the flexor perforans digitorum. It terminates in the anterior and posterior tibial arteries. [Illustration: FIG. 68.—Blood-vessels and nerves of the fore limb. Inside view. 1, Vena humeri profunda. 2, Brachialis longus inferior. 3, Brachialis profunda. 4, Radial artery. 6, Ulnar artery. 7, Ulnar arterial branch to thumb. 8, Digital branch of ulnar artery. 9, Ulnar artery. ] The first, the _tibialis postica_ (Fig. 69, No. 12) passes between the gastrocnemius and the deep flexors giving off branches in its course to the skin and to other parts, and disappears shortly below the intertarsal joint.