382 AZYGOS VEINS. 



The Lumbar veins, three or four in number on each side, collect the 

 venous blood from the muscles and integument of the loins, and from 

 the spinal veins: the left are longer than the right from the position 

 of the vena cava. 



The Right spermatic vein is formed by the two veins which return 

 the blood from the venous plexus, situated in the spermatic cord. 

 These veins follow the course of the spermatic artery, and unite to 

 form the single trunk which opens into the inferior vena cava. The 

 left spermatic vein terminates in the left renal vein. 



The Ovarian veins represent the spermatic veins of the male, and 

 collect the venous blood from the ovaries, round ligaments, and Fallo- 

 pian tubes, and communicate with the uterine sinuses. They terminate 

 as in the male. 



The Renal or emulgent veins return the blood from the kidne} r s ; 

 their branches are situated in front of the divisions of the renal 

 arteries, and the left opens into the vena cava somewhat higher than 

 the right. The left is longer than the right in consequence of the 

 position, of the vena cava, and crosses the aorta immediately below the 

 origin of the superior mesenteric artery. It receives the left spermatic 

 vein, which terminates in it at right angles: hence the more frequent 

 occurrence of varicocele on the left than on the right side. 



The Supra-renal veins terminate partly in the renal veins, and partly 

 in the inferior vena cava. 



The Phrenic veins return the blood from the ramifications of the 

 phrenic arteries ; they open into the inferior cava. 



The Hepatic veins form two principal trunks and numerous smaller 

 veins which open into the inferior cava, while that vessel is situated 

 in the posterior border of the liver. The hepatic veins commence in 

 the liver by minute venules, the intralobular veins, in the centre of 

 each lobule ; these pour their blood into larger vessels, the sublobular 

 veins; and the sublobular veins constitute by their convergence and 

 union, the hepatic trunks, which terminate in the inferior vena cava. 



AZYGOS VEINS. 



The azygos veins form a system of communication between the su- 

 perior and inferior vena cava, and serve to return the blood from that 

 part of the trunk of the body in which those vessels are deficient, on 

 account of their connection with the heart. This system consists of 

 three vessels, the 



Vena azygos major, 



Vena azygos minor, 



Superior intercostal vein. 



The Vena azygos major commences in the lumbar region by a com- 

 munication with the lumbar veins; sometimes it is joined by a branch 

 directly from the inferior vena cava, or by one from the renal vein. 



