THE VEINS. 247 



The posterior caval vein is a median vein which, commencing be- 

 tween the kidneys, runs forwards to open into the posterior end 

 of the Sinus venosîts. It receives the hepatic, renal, and ovarian or 

 spermatic veins. 



a. The hepatic veins (Fenae Âej)ai/cae), (Fig-. 164 v.k.) are two in 

 number, one from either side of the liver ; they open into the 

 posterior caval vein near the Siwi-S' vefiosns. 



ta. The renal veins [Venae rénales or Venae revehentes), (Fig. 

 163 r) are fuur or five small vessels on each side; they pass from 

 the inner border of the kidney inwards and forwards, to form, 

 by their union, the posterior caval vein. The most anterior receive 

 branches from the fat-bodies (see kidney). 



c. The spermatic or ovarian veins are four or five in number on 

 each side ; they open into the posterior caval vein between the renal 

 veins. 



3. The Portal Systems. 



[There are, in the frog, two portal systems ; the renal and the 

 hepatic. Each of these receives vessels which are derived, directly 

 or indirectly, from the veins of the hinder extremity. 



The femoral vein on entering the pelvis divides to form two 

 branches ; an iliac vein placed dorsally, and a pelvic vein placed 

 ventrally; the two pelvic veins converge to the middle line of 

 ventral wall of the abdomen, where they unite to form the ante- 

 rior abdominal vein.] 



a. The renal portal vein ( Fewa renalis advehens princeps), (Fig. 

 163 «). This vein is formed by the union of the sciatic and the 

 iliac veins ; it courses forwards to the outer border of the kidney, 

 and is distributed, by numerous branches, to that organ, chiefly 

 on its dorsal surface. It receives the following veins : — 



(i) The iliac vein {Vena iliaca externa); this is the dorsal branch 

 formed by the bifurcation of the femoral vein. 



(2) The sciatic vein [Vena iscliiadica), (Figs, 163 and 165 i) 

 arises at the popliteal space, courses upwards in company with the 

 sciatic nerve between the M. semitendinosus and the M. hiceiis, then 

 passes, still with the nerve, between the M. vastus externus and the 

 M. pyramid alls into the pelvis. It continues forwards to join the 

 iliac vein. At the root of the thigh this vein communicates with 

 the femoral vein by the Eamns communicans iliacus. 



