THE DEEP VEINS OF THE LOWER LIMB. 539 



the artery through the opening in the adductor magnus, and becomes continuous 

 with the femoral vein. The popliteal vein has two or three valves. 



In addition to the large popliteal trunk, there are two smaller veins accompanying the 

 artery, one on. each side, formed respectively by the continuation upwards of the internal and 

 external lower articular veins, which are joined by some muscular branches. 



Varieties. The union of the veins which form the popliteal is often farther up than 

 usual, and the lower part of the artery is then accompanied by two large veins. This arrange- 

 ment in some rare cases extends to the entire length of the artery. 



The femoral vein extends, like the artery which it accompanies, through the 

 upper three-fourths of the thigh, and terminates at Poupart's ligament in the external 

 iliac vein. Placed behind and at first somewhat to the outer side of the artery, it 

 gradually inclines inwards, and on reaching Poupart's ligament lies on the inner 

 side, on the same plane with the artery, from which it is separated only by a slight 

 partition of the membranous sheath investing both vessels. In the lower part of its 

 course, the vein receives the branches which accompany the offsets of the superficial 

 femoral artery ; in the upper part, the deep femoral (profunda) rein opens into it, 

 having first received the venae comites of the branches derived from 'the deep 

 femoral artery ; and near its termination it is joined by the internal saphenous vein. 

 The femoral vein contains three or four valves, one of which is usually placed imme- 

 diately above the entrance of the profunda vein. In most cases there is another 

 valve (the ilio-femoral valve of Bennett) near Poupart's ligament, either in the upper 

 end of the femoral vein, or in the lower part of the external iliac. 



The femoral artery is also accompanied in Hunter's canal by two or three small veins, 

 which adhere closely to it, and often receive some of the muscular branches : they open into 

 the main trunk before the junction of the profunda vein. 



Varieties. The femoral vein occasionally pursues a course different from that of the 

 artery along the thigh. Extending upwards from the popliteal space, the vein in such cases 

 perforates the adductor magnus above the ordinary position, and, joining with the deep 

 femoral vein, first approaches the femoral artery at the groin. The same vein is sometimes 

 double in a small part, or more rarely in almost its whole length, a condition which may be 

 explained as resulting from the enlargement of one of the small companion veins. 



The external iliac vein is the continuation of the femoral vein from Poupart's 

 ligament to the junction of the internal iliac vein, in the neighbourhood of the 

 lumbo-sacral articulation. It is at first internal to the artery, but as it ascends it 

 gradually inclines to the back of that vessel. It frequently contains one valve, 

 rarely two. 



Near its commencement at Poupart's ligament, the external iliac vein receives 

 the deep circumflex iliac and epigastric veins (v. p. 484), corresponding to the 

 arteries of the same name, and also a pubic vein, which ascends from the obturator 

 vein in the thyroid foramen, and frequently constitutes the principal termination of 

 the latter vessel. 



VEINS OF THE PELVIS. 



The internal iliac vein is formed by the union of branches which accompany 

 most of the branches of the internal iliac artery. The umbilical vein of the foetus, 

 however, which in the cord accompanies the corresponding arteries, diverges from 

 these arteries within the body, and passes upwards to the liver. The internal iliac 

 vein lies behind and somewhat to the inner side of the artery, and, after a short 

 course upwards to the margin of the pelvis, joins with the external iliac vein, to 

 form the common iliac. No valves are found in the trunk of the internal iliac vein, 

 but they exist in its branches. 



Tributaries. The tributaries of the internal iliac vein correspond in general to 

 the various branches of the internal iliac artery, with the exception that the internal 



