The vessels starting at the foot are the anterior and posterior tibial veins, which unite just below the knee to form the popliteal vein, in the popliteal space. Another vein starts from the foot and runs into the popliteal vein called the external short saphenous. Starting also at the foot and running into the posterior tibial vein is the peroneal vein. The popliteal vein after leaving the popliteal space is known as the femoral vein as it passes up the leg, to Poupart's ligament. Another vein, the internal long saphenous, starts at the foot, and runs into the femoral vein about an inch below Poupart's ligament. After passing beneath Poupart's ligament the vessel is called the external iliac. Coming from the organs of the pelvic cavity is the internal iliac, which joins with the external iliac vein to form the common iliac vein. The right and left iliac veins join opposite the umbilicus to form the ascending vena cava. The ascending vena cava passes upward to the right of the vertebral column through the diaphragm and enters the right auricle of the heart by means of the eustachian valve. [Illustration: FIG. 38—The superficial veins of the arm. (Gray)] In the forearm are the radial veins on the thumb side of the hand, the ulnar veins on the little finger side of the hand, and the median vein just between the radial and ulnar veins. The median vein divides into the median cephalic vein and the median basilic. The median cephalic vein unites with the radial vein to form the cephalic vein, which runs up the back part of the arm and finally empties into the subclavian vein. The median basilic unites with the ulnar vein to form the basilic, which runs up the inner part of the arm between the biceps and triceps muscles. The deep brachial veins or the vena comites, two in number, which follow the brachial artery, run into the basilic vein. When the basilic vein arrives at the axillary space it takes on the name of the axillary vein, and as the vessel passes beneath the subclavian bone, it becomes the subclavian vein. The right and left subclavian veins with the right and left internal jugular veins from each side of the head form the right and left innominate veins, which unite to form the descending vena cava, which runs into the right auricle of the heart. [Illustration: FIG. 39—Vertical section of the skull, showing the sinuses of the dura mater. (Gray)]