THE POSTEBlOn VENA CAVA. 621 



B. Small Mesenteric or Posterior Mbsahaio Vein (Figs. 293 43 • 

 294, 12). — This vessel commences above the rectum, near the anus by 

 large liaemorrhoidal branches which communicate with the homonymous 

 ramuscles of the internal pudic. It is directed forwards, between the two 

 layers of the second mesentery, along the small mesenteric artery, which it 

 passes, and extends to the great mesenteric artery, on the left side of which 

 it imites with the splenic vein, before opening into the anterior mesaraic to 

 form the vena portse. In its course it receives all the satellite venous 

 branches of the divisions of the artery of the same name, and whose 

 arrangement is similar to that of the arterial ramifications. 



C. Splenic Vein (Fig. 294, 13).— This is an enormous canal which 

 follows the splenic artery, and comports itself exactly like it. It begins by 

 the left gastro-epiphio vein (Fig. 294, 14) anastomosing in arcade with the 

 right gastro-epipioic, receiving on its track gastric, splenic, and epiploic 

 branches, and joining the small mesaraic after passing above the left ex- 

 tremity of the pancreas, and obtaining the posterior gastric vein (Fig. 294, 16). 



2. Collateral Affluents of the Vena Portce. 



A. Eight Gastro-epiploic Vein (Fig. 294, 15). — We already know that 

 the hepatic artery, before entering the liver, gives off pancreatic branches, a 

 pyloric branch, and a gastro-epiploic division, which in turn detaches a small 

 duodenal artery ; the vessel described as the right gastro-epiploic vein cor- 

 responds, in every respect, to all these collateral ramifications of the hepatic 

 artery. 



This vein, then, has its origin from around the great curvature of the 

 stomach, but at an undetermined point, as it forms an anastomotic arch with 

 the left gastro-epiploic vein. Posteriorly, it crosses the dilatation at the 

 origin of the duodenum, receives the pyloric, duodenal, and pancreatic veins, 

 and opens into the vena portse after traversing the pancreas. 



B. Anterior Gastric Vein. — Satellite of the homonymous artery, 

 this vein joins the vena port© separately, after the entrance of that vessel 

 into the great posterior fissure of the liver, and when very near the terminal 

 extremity of that fissure. 



renal veins. 



Two in number, like the arteries they accompany, these veins are dis- 

 tinguished by their enormous volume and the tenuity of their walls. The 

 left, having to cross the abdominal aorta before entering the vena cava, is 

 longer than the right. They receive the majority of the veins from the 

 suprarenal capsules (293, 10). 



SPEEUATIC VEINS. 



These vessels correspond to the great spermatic arteries of the male, and 

 the utero-ovarian arteries of the female. 



Testicular vein. — The radicles which constitute this vein present, at their 

 emergence from the superior border of the testicle, a flexiform and very 

 complicated arrangement, enlacing, turning, and inflecting themselves in a 

 thousand ways around the convolutions of the groat spermatic artery, and 

 ascending in this manner towards the neck of the vaginal sheath (abdominal 

 ring), which they pass through usually after joining to form two trunks. 

 These rise towards the sublumbar region, beneath the peritoneum, in a fold 

 of which they are at first included ; they communicate with one another in 



