THE INFERIOR CAVAL SYSTEM. 903 



5. The Middle Suprarenal Veins. — ^The middle suprarenal veins (vv. 

 suprarenales ) are the principal veins of the suprarenal bodies, from which, however, 

 the superior suprarenals, emptying into the phrenics, and the inferior, opening 

 into the renals, also arise. Each vein occupies a groove on the anterior surface 

 of the suprarenal body, and descends obliquely inward to open on the right 

 side into the inferior vena ca\'a abo\'e the right renal, and on the left side into the 

 left renal. 



6a. The Spermatic Veins. — The spermatic veins (vv. spermaticae) begin at 

 the internal abdominal ring, whence they pass upward and inward along with the 

 spermatic arteries and are the continuation upward of the venous plexuses which 

 surround the spermatic cords. 



Each of these plexuses has its origin in the testicular veins ( vv. testiciilares) 

 which return the blood from the tunica albuginea testis and from the seminiferous 

 tubules, these latter branches passing towards the hilum of the organ in the trabeculae. 

 They make their exit from the testis at about the middle of its superior border, and 

 are joined very shortly by the veins of the epididymis. They are then continued 

 up the spermatic cord in the form of from ten to twenty flexuous stems, which 

 anastomose abundantly to form what is termed the pampiniform plexus (plexus 

 pampiaiformis), surrounding the spermatic artery. As the cord enters the inguinal 

 canal the plexus is reduced to some three or four stems, which, at the internal 

 abdominal ring, become the spermatic veins. 



These are two or three stems which anastomose abundantly with one another 

 and consequently present a plexiform arrangement. They surround the abdominal 

 portion of the spermatic artery and, shortly before reaching their termination, unite 

 to a single stem, which on the right side opens at an acute angle into the vena cava 

 inferior below the right renal vein, while on the left side it opens almost at a right 

 angle into the lower border of the left renal vein. 



The spermatic veins proper possess no valves, except that there is usually 

 a pair at the entrance of the right vein into the vena cava. In the stems of the 

 pampiniform plexus, however, valves are usually to be found, but they are very 

 frequently insufBcient. 



Tributaries. — The spermatic veins receive a ureteric branch from the lower part of the 

 ureter and also peritoneal branches and renal branches from the adipose capsule of that organ, 

 hi the scrotum the pampiniform plexus makes connections with the branches of the external pudic 

 veins, and at their entrance into the external abdominal ring the two plexuses of opposite sides 

 are connected by transverse anastomoses which pass in front of the symphysis pubis. A deeper 

 transverse anastomosis also occurs between the two spermatics as they emerge from the internal 

 abdominal rings, and they communicate by means of their peritoneal branches with the branches 

 of the right and left colic veins. 



Variations. — Occasionally the left vein as well as the right opens directly into the vena cava, 

 and in cases in which that vessel is situated upon the left side it is the left vein which opens 

 directly into it, the right one opening into the right renal vein. They communicate sometimes on 

 one side or the other with a lumbar vein or with the middle suprarenal, and the left vein has 

 been observed to open into the hemiazygos. 



The spermatic veins are very apt to become varicose, and it is well known that this con- 

 dition is more apt to occur in the left vein than in the right. Various reasons have been assigned 

 for this difference in the two veins, the chief of these being (i) that the left vein opens at prac- 

 tically a right angle into the renal, while the right opens at an acute angle into the vena cava ; 

 (2) the left vein is destitute of valves at its opening into the renal, while the right one usually 

 possesses a pair at its orifice ; and (3) that the left vein in its course up the abdominal wall lies 

 beneath the sigmoid colon, while the right has only coils of the small intestine with their more 

 fluid contents in front of it. 



6b. The Ovarian Veins. — The ovarian veins (vv. ovaricae) correspond to 

 the spermatic veins of the male. They take their origin from the veins which 

 issue at the hilum of the ovary and are also connected by wide anastomoses 

 with the veins of the fundus of the uterus. They form a close plexus, the pam- 

 piniform plexus (plexus pampiniformis), which accompanies the ovarian artery 

 between the two layers of the broad ligament parallel with the Fallopian tube,  

 receiving branches from the latter structure and from the round ligament of the 



