986 THE VASCULAK SYSTEM. 



extremity ; it is continued proximally, through the thigh, as the femoral vein, and 

 along the upper margin of the pelvis minor as the external iliac vein, which 

 terminates by uniting with the hypogastric vein to form the common iliac vein. 



Further, the superficial veins of the upper limb are more numerous than those 

 of the lower limb, for in the arm there are two main superficial veins, and in the 

 thigh only one. 



In the upper limb the blood which passes through the superficial veins is poured 

 into the efferent trunk vein at the root of the limb that is, into the axillary vein ; 

 but in the lower limb the blood from the superficies of the lateral parts of the leg 

 and foot passes into the commencement of the main efferent vein, the popliteal 

 vein, at the middle of the limb that is, in the region of the knee, whilst the 

 blood from the superficial parts of the medial aspect of the lower limb is poured 

 into the femoral vein near the root of the limb in the upper part of the femoral 

 trigone. 



In addition to the above-mentioned differences in the general arrangement of the 

 veins of the superior and the inferior extremities, it must be noted also that in the 

 superior extremity all the blood of the limb, both that from the shoulder-girdle region 

 as well as that from the free portion of the limb, is returned to the main efferent 

 venous trunk ; but in the inferior extremity the greater part of the blood from 

 the region of the pelvic girdle, and a considerable portion from that of the thigh, is 

 returned by the glutseal, obturator, and pudenda! veins to the hypogastric vein, 

 which is not the main efferent vein of the inferior extremity. 



THE DEEP VEINS OF THE INFERIOR EXTREMITY. 



All the arteries of the lower limb, except the popliteal and femoral trunks, are 

 accompanied by two vence comites. They usually lie one on each side of the 

 artery ; they are connected with one another by transverse channels which pass 

 across the line of the artery, and they are provided with numerous valves. 



Vena Poplitea. The popliteal vein (Figs. 776, 780, 781) is formed, at the 

 distal border of the popliteus muscle, by the union of the venae comites of the 

 anterior and posterior tibial arteries. At its commencement it lies to the medial 

 side of and somewhat superficial to the popliteal artery, and to the lateral side 

 of the tibial (O.T. internal popliteal) nerve. As it runs through the popliteal 

 fossa it inclines towards the lateral side of the artery, and in the middle of the 

 space it is directly posterior to the artery, separating the artery from the tibial 

 nerve, which is still more posterior, whilst at the proximal end of the space it is to 

 the lateral side of the artery, and still between it and the tibial nerve. It then 

 passes through the adductor magnus muscle and becomes the femoral vein. 



The popliteal vein, which is provided with two or three bicuspid valves, is closely 

 bound to the artery by a dense fascial sheath. Not uncommonly there are one or 

 more additional satellite veins which anastomose with the popliteal vein, and in 

 those cases the artery is more or less completely surrounded by venous trunks. 



Tributaries. In addition to the vense comites of the anterior and posterior tibial 

 arteries, it receives tributaries which correspond with the branches of the popliteal artery, 

 and it also receives one of the superficial veins of the leg, viz., the small saphenous vein. 



Vena Femoralis. The femoral vein is the direct continuation of the popliteal 

 vein. It commences at the junction of the middle and distal thirds of the thigh, 

 at the opening in the adductor magnus muscle. It then ascends, through adductor 

 canal (Hunter's), and through the femoral trigone, and terminates, a little to the 

 medial side of the middle of the inguinal ligament (Poupart's), by becoming the 

 external iliac vein. 



In the adductor canal it lies at first postero-lateral to the femoral artery, and 

 anterior to the adductors .magnus and longus which separate it from the profunda 

 vessels. In the distal part of femoral trigone it is postero-medial to the artery, 

 and immediately anterior to the profunda vein which separates it from the 

 profunda artery, but in the proximal part of the femoral trigone it is directly on 

 the medial side of the femoral artery. About 37 mm. (one and a half inches) below 



