1. =V. sacralis media= (Fig. 126, _o_).--This follows the course of the corresponding artery and usually enters the left common iliac. 2. =V. hypogastrica= (or =iliaca interna=) (_z_).--The hypogastric or internal iliac vein joins the medial side of the external iliac to form the common iliac (_w_). Its branches follow the branches of the corresponding artery except that the vein from the bladder (umbilical vein) joins the =V. hemorrhoidalis media=. Also the =vena glutea inferior= receives a large superficial communicating branch (Fig. 163, _k_′) from the =vena saphena parva=. This branch leaves the saphena parva (Fig. 163, _k_) at the popliteal space, and passes over the lateral surface of the biceps muscle to its proximal end. Here it passes between the biceps and caudofemoralis to join the vena glutea inferior. 3. =V. iliaca externa= (Fig. 127, page 310).--This vein follows the corresponding artery, collecting the blood from the posterior extremity. Its branches are the same and have in general the same distribution as those of the artery. The vein has, however, certain branches in addition to those of the artery, resulting in a somewhat different general arrangement of vessels; it will be necessary therefore to give an account of the system of veins from the foot and lower leg. The blood is collected from the foot into two sets of veins which may be distinguished as the _deep_ and the _superficial_ sets. The veins of the deep set are those which accompany the branches of the popliteal and anterior tibial arteries. Those of the superficial set are larger and carry most of the blood. On the dorsum of the foot blood is collected from the third, fourth, and fifth digits by two or three superficial metatarsal veins, which unite opposite the proximal end of the metatarsus into a single vein. This receives a similar branch coming from the dorsum of the second digit, and has numerous branches in the ankle region which form here a network, communicating with the vena saphena parva (Fig. 163, _k_), and with branches from the plantar side of the foot. From this network two or three main veins pass proximad on the medial side of the leg, along with the branches of the arteria saphena, and unite with a similar vein from the plantar side of the foot to form the vena =saphena magna= (Fig. 127, _k_, page 310), which accompanies the arteria saphena to join the femoral vein (_a_).