140 INNERVATION. [CHAP. XXI. 



The nervous plexuses in the abdomen are extremely complicated 

 and numerous. They are principally derived from two great gan- 

 glia, situate on each side of the cseliac axis, in front of the aorta. 

 These ganglia are semilunar in shape, convex downwards and out- 

 wards, they unite below the cseliac axis; and chiefly from their 

 convex border, a vast radiation of plexiform nerves takes place, 

 which follow the course of, and entwine around the branches of the 

 caeliac axis, and of other branches of the aorta. To this great ra- 

 diation anatomists have given the name of solar plexus and the 

 conjoint semilunar ganglia must be looked upon as the great cen- 

 tre, the sun of the abdominal sympathetic system. 



Plexuses radiate from this source around the principal branches 

 of the aorta, and they are named after the arteries which they ac- 

 company. They are the diaphragmatic or phrenic ; the supra-renal; 

 the (cceliad, which divides into the hepatic, gastric and splenic ; the 

 superior mesenteric, from which proceed nerves, which, with others 

 from the lumbar portion of the sympathetic, form the inferior me- 

 senteric plexus ; and the renal plexuses, from which chiefly are de- 

 rived the spermatic plexuses, destined to the ovaries in the female, 

 and the testicles in the male. Of these plexuses the following are 

 deserving a more particular notice : 



The gastric plexus accompanies the coronary artery of the 

 stomach, and passes along the lesser curvature of that organ. With 

 the gastric branches of the vagus it forms the principal nervous 

 supply to the stomach, which is completed by an off-shoot sur- 

 rounding the right gastro-epiploic artery from the hepatic plexus, and 

 by other nerves from the same plexus distributed chiefly to the 

 , and by branches from the splenic plexus. 



The hepatic plexus follows the hepatic artery and the vena portae 

 into the substance of the liver ; it is joined by a branch of the 

 vagus ; and it gives off nerves to the stomach, and to the pancreas. 



The splenic plexus surrounds the splenic artery, supplies the pan- 

 creas, and the left extremity of the stomach, by entwining round 

 the left gastro-epiploic artery, and by direct branches to the great 

 cul de sac of the stomach. These nerves then follow the branches 

 of the splenic artery into the spleen. 



The superior mesenteric plexus supplies the greatest portion of 

 the intestinal canal, entwining around the superior mesenteric 

 artery and its ramifications. Connected with it are some ganglia 

 of variable size, called cceliac or mesenteric ganglia. From these 

 ganglia, and from the upper part of the plexus, nerves are derived 

 to the pancreas, and to the duodenum. 



