VISCERAL PLEXUSES OF SYMPATHETIC. 443 



c. The superior htemorrhoidal artery (e) enters between the layers of 

 the meso-rectum, and is distributed to the lower part of the great intes- 

 tine : it will be described in the dissection of the pelvis. 



The inferior mesenteric vein (fig. 146, d) begins in the part of the great 

 intestine to which its companion artery is distributed, and ascends along 

 the psoas muscle to open into the splenic vein beneath the pancreas. Oc- 

 casionally it joins the superior mesenteric vein. 



Both mesenteric veins are without valves, and may be injected from the 

 trunk to the branches, like an artery. 



Lymphatic glands are ranged along the descending colon and the sig- 

 moid flexure. The absorbents of the intestine, after passing through 

 those glands, enter the left lumbar lymphatic glands. 



SYMPATHETIC NERVE. The following plexuses of the sympathetic 

 on the vessels, viz., superior mesenteric, aortic, spermatic, and inferior 

 mesenteric, are derived from the solar plexus beneath the stomach. The 

 remaining portion of the sympathetic nerve in the abdomen will be subse- 

 quently referred to. 



Dissection. On the two mesenteric arteries the dissector will have 

 made out, already, the plexuses of nerves distributed to the intestinal tube 

 beyond the duodenum. 



He has now to trace on the aorta the connecting nerves between the 

 mesenteric plexuses, by taking the peritoneum from the aorta between the 

 mesenteric vessels. From the upper part of the aortic plexus an offset is 

 to be followed along the spermatic artery ; this may be done, on the left 

 side, where the vessel is partly laid bare. 



By removing the peritoneum from the front of the sacrum, and follow- 

 ing downwards, over the iliac arteries, the nerves from the aortic plexus 

 and the lumbar ganglia, the dissector will arrive at the hypogastric plexus 

 of the pelvis, opposite the top of the sacrum. 



The superior mesenteric plexus is a large offset, and is distributed to 

 the same extent of the intestinal tube as the mesenteric artery. The 

 nerves surround closely the artery with a sheath, but near the intestine 

 some of them leave the vessels, and divide and communicate before enter- 

 ing the gut. Branches. The secondary plexuses are the same as the off- 

 sets of the artery, viz., intestinal nerves to the small intestine ; and an 

 ileo-colic, a right colic, and a middle colic plexus to the large intestine. 



The aortic plexus is the network of nerves covering the aorta below 

 the superior mesenteric artery ; it is stronger on the sides than the front 

 of the aorta, in consequence of its receiving accessory branches from the 

 lumbar ganglia, especially the left. At the upper part the plexus derives 

 an offset, on each side of the aorta, from the solar and renal plexuses. 1 1 

 ends inferiorly, on each side, in branches which cross the common iliac 

 artery, and enter the hypogastric plexus of the pelvis. From it offsets 

 are furnished to the spermatic and inferior mesenteric arteries. 



The spermatic plexus, formed by roots from both the aortic and the 

 renal plexus, runs on the spermatic artery to the testicle ; in the cord it 

 joins other filaments on the vas deferens. 



In the female, the nerves on the ovarian (spermatic) artery are furnished 

 to the ovary and the uterus. 



The inferior mesenteric plexus supplies the part of the intestinal tube 

 to which the artery is distributed. This plexus is furnished from the left 

 part of the aortic plexus ; and the nerves composing it are whiter and 

 larger than in either of the preceding plexuses of the sympathetic. Near 



