THE POSTERIOR VENA CAVA. 623 



The trunk resulting from the union of these different branches is usually 

 very short ; it may even be altogether absent, and we then see its con- 

 stituent veins open into the common iliac vein by forming two or three 

 separate groups situated very close to each other. 



2. External Iliac Vein. 



This vein constitutes the principal root of the pelvi-crural trunk, which 

 is but a continuation of it, the internal iliac being only, properly speaking, 

 a collateral affluent of the single canal represented by the external and 

 common iliac veins. 



Situated behind the crural arterial trunk, this external iliac vein com- 

 mences at the anterior border of the pubis, where it is directly continued, 

 without any line of demarcation, by the femoral vein. 



The only important vessel it receives on its course is the iliac circumflex 

 vein, which, however, opens more frequently into the common than the 

 external iliac. 



3. Femoral Vein. 



Continuous by its superior extremity with the external iliac vein, and 

 inferiorly with the popliteal, this femoral vein is remarkable for its large 

 volume, and closely follows the artery of the same name throughout its 

 extent (Fig. 293, 5). 



The collateral affluents it receives in its course are distinguished by 

 their number and considerable volume. They are : 



1. The satellite veins of the muscular arteries. 



2. The internal saphena vein, which will be again referred to in describing 

 the superficial veins of the leg. 



3. The prepubic vein, formed by the posterior abdominal and the branches 

 of the internal pudic. The latter are very numerous and large, and anas- 

 tomose with each other, forming between the thighs, in the texture of the 

 scrotum and sheath, and above the penis, a very rich network which com- 

 municates behind with the cavernous veins. This network only sends a 

 small trunk into the inguinal ring, along the external pudic artery ; in its 

 middle part it opens into an enormous branch which traverses the ring in 

 the sartorius muscle, and is lodged in the inferior groove of the pubis to 

 join the femoral vein. 



One of these external pudic veins represents the subcutaneous abdominal 

 vein, and communicates with the subcutaneous thoracic vessel. 



All these branches in the female show an analogous disposition, 



4. Popliteal Vein. 



Satellite of the popliteal artery, this vein is formed by the union of the 

 anterior and posterior tibial veins. 



Among the branches it receives on its course, the femoro-popliteal vein 

 may be particularly noted ; this accompanies the artery of the same name, 

 and joins the external saphena before opening into the popliteal vein. 



5. Deep Veins of the Leg. 



These are two in number : the anterior and posterior tibial. 

 A. ANTERIOR TIBIAL VEIN (Fig. 278, 5). Placed beside the homo- 

 nymous artery, often double, always very ample, this vein originates on the 



