TRIBUTARIES OF THE INFERIOR VEXA CAVA 633 



perfect pair at the termination of each spermatic vein. On the left ^ide. hov/ever, 

 the terminal valve may l»e wanting. 



(4) The ovarian veins hegin as the panii»inif<)rm ])lexus near tlie (tvarv, 

 between the layers of the broad ligament. This i)lexiis communicates freely Avith 

 the uterine plexus of veins, and with the plexus of veins which extends from the 

 hilum of the ovary into the ovarian ligament (the ovarian bulb). After passing 

 from between the layers of the broad ligament, the plexus unites to form at first 

 two and then a single vessel, which accompanies the ovarian artery, following a 

 similar course to the spermatic veins in the male. The right ovarian vein opens 

 into the inferior vena cava; the left into the left renal. They usually contain 

 imperfect valves in their i)lexiform part, and a perfect valve where they join the 

 vena cava and renal vein respectively. 



(5) The lumbar veins. — There are usually fovn- lumbar veins on each side 

 corresponding to the lumbar arteries. The main trunks of these veins, which lie 

 beside the bodies of the lumbar vertebrae, are formed by the union beneath the 

 psoas of anterior and posterior branches. The anterior branches collect the 

 blood from the front and lateral walls of the abdomen. They conmnmicate in 

 front with the internal manmiary and epigastric veins, and then run backwards 

 Ijetween the alxlominal muscles in company with the anterior branches of the luml)ar 

 arteries to their confluence with the posterior branches. The posterior branches 

 collect the blood from the loins and muscles of the back, and correspond to the 

 ]>osterior or dorsal division of the lumbar arteries. They receive connnuni- 

 cating branches from the dorsal spinal plexus and from the verteVjral canal, and 

 pass forwards between the transverse processes to join the anterior branches. The 

 trunk lumbar veins are connected beneath the psoas muscle by vertical l)ranches, 

 which cross in front of the transverse processes. The last lumbar vein is variously 

 joined below b}^ a vertical branch to the common iliac, internal iliac, lateral sacral 

 or ilio-lumbar vein, and the first lumbar vein is similarly connected al)Ove with the 

 connnencement of the vena azygos major on the right, and the vena azygos minor 

 on the left side. The vertical vein thus formed is known as the ascending lumbar 

 vein, and is regarded by some morphologists as the remains of the primitive or 

 cardinal vein of the emI)rvo. The trunk lum])ar veins run uj) ])eneath the tendin- 

 ous arches of the })soas on the sides of the bodies of tlie vertebra? in company with 

 the lumbar arteries and branches of the sympathetic nerve, and end in the inferior 

 vena cava on its posterior aspect. The left veins are longer than the right, and 

 pass behind the aorta. 



(G) The phrenic veins, or inferior phrenic veins as they are sometimes 

 called, follow the course of the phrenic arteries: the right opens into the vena cava 

 direct; the left into the suprarenal, the left renal, or tlie vena cava. 



(7) The hepatic veins, the largest tributaries of the vena cava, return the 

 Itlood from the liver. C'onnneneing in the substance of the liver (see Liver), they 

 converge as they approach its posterior surface, and unite to form two or three 

 large branches, which open into the vena cava as it lies in the groove or canal in 

 that organ. Some smaller vessels from the lobulus 8i)igelii, and other parts of the 

 liver in the neighbourhood of the caval groove, open directly into the vena cava. 

 The hepatic veins contain no valves, but, in consequence of those from the riglit 

 and left lobe of the liver opening obli(iuely into the vena cava, ])resent a .semilunar 

 fold at the lower margins of their orifices. 



Chief V(iri(it'n>ti^ in tJie Inferior ]'eii(i Ctira 



(1) The inferior vena cava, in oases of transpo-sition of tlu' viscera, may lie on the left siile 

 of the aorta. (2) Without tninsi>osition it may also lie to the left of the aorta, emssinir to the 

 riirht to .irain the eaval oi)eniiiir immediately below the (]iaiihra,i:in, or after receivin.ir the leit renal 

 vein. (H) It may he doulile. the left cava tlien usually passinir across tlie aorta into the riuht 

 after receivinii the left renal vein. A commuiiieation lictweeii the right and left veins in the ])osi- 

 tion of the normal left eominoii iliac vein may or may not then exist. (4) The inferior vena cava 

 may be absent, the blood from the lower extremities passing by a large vein in the position of the 

 ascending lumbar and azygos veins throuah the diai>hrai:m to open into the suiierior vena cava. 

 The hepatic veins then "open directly into the right auricle thmugli the normal eaval opening 

 in the diajihragm. (.')) The inferior vena cava may receive the left si.ermatie vein, (t.) Tt may 

 receive a left accessory renal vein i)assing behind the aorta, and into this the usual tributaries 



