494 THE INFEEIOR VENA CAVA. 



a. — Tlic middle sacral vein, taking its course upwai'ds on the front 

 of the sacrum, opens into the left common iliac vein, or into the com- 

 mencement of the vena cava. 



1). — T]ie lumbar veins correspond in number with the arteries of tho 

 same name : they commence by small posfrrior branches in the muscles 

 of the back ; and by others from the -walls of the abdomen, where they 

 communicate with the epigastric and other veins in the neighbour- 

 hood. Having reached the spine, they receive branches from the 

 spinal plexuses, and proceed forward upon the bodies of the vertcbrte, 

 behind the ]^)6oas muscle : those on the left side passing l^ehind the 

 aorta, terminate in the back of the vena cava. Some of these veins 

 are frequently found to unite into a single trunk before their termina- 

 tion. The "lumbar veins of the same side communicate with each 

 other by branches which cross in front of the transverse processes. 

 Not unfrequently a branch of this description is met with called the 

 ascending himlar vein, which connects more or less completely the 

 common iliac vein, the ilio-lumbar and lumbar veins, and the azygos 

 vein. 



c. — The spermatic veins, proceeding upwards from the testicle and 

 forming part of the constituents of the spermatic cord, enter the 

 abdomen, and ascend on the psoas muscle behind the peritoneum. 

 Below the abdominal ring there are numerous convoluted branches 

 forming the spermatic jJlexus (plexus pampiniformis). These branches 

 gradually unite and form a single vessel, Avhich opens on the right side 

 into the lower vena cava, and on the left into the renal vein. The 

 spermatic veins sometimes bifurcate before their termination, each 

 division opening separately ; in this case the veins of the right side 

 may be found communicating with the vena cava and the renal vein. 



In the female the ovarian veins have the same general course as the 

 ovarian arteries ; they form a plexus near the ovary (ovarian or pam- 

 piniform plexus) in the broad ligament, and communicate with the 

 uterine plexus. 



Valves exist in the spermatic veins in man (Monro) ; and in esccD- 

 tional cases they have been also seen in the ovarian veins (Theile). 



d. — The renal or emulgent veins are short but of very considerable 

 size. That of the left side is longer than that of the right, and passes 

 in front of the aorta. They join the vena cava at nearly a right angle. 

 The renal veins usually receive branches from the suprarenal capsules ; 

 the left has also opening into it the spermatic vein of the same side. 

 A valve is usually found at the orifice of the left spermatic vein, or in 

 the renal vein within a quarter of an inch from the orifice of the sper- 

 matic. (Ptivington. Journ. of Anat. Vol. VIL, p. 163.) 



e. — The capsular or suprarenal veins, though actually small, are, 

 relatively to the organs from which they arise, of considerable size. 

 On the right side the vein ends in the vena cava, and on the left in the 

 renal or phrenic vein. 



/. — The phrenic veins follow exactly the course of the arteries sup- 

 plied to the diaphragm by the abdominal aorta. 



g. — The hepatic veins return from the liver the blood sent to that 

 organ by the portal vein and hepatic artery. They converge to the 

 groove in v,liich the inferior vena cava lies, and pass at once obliquely 

 into that vein. There are usually three sets of hepatic veins pro- 

 ceeding to this common point : those from the right and left lobes are 



