300 NERVOUS SYSTEM. 



These three nerves, the two splanchnics and the sympathetic, 

 make their entry into the abdomen along the under surface ot" 

 the crus of the diaphragm. The splanchnics are then thus 

 distributed : — The greater splanchnic turns downward, and con- 

 tributes its branches to the formation of the semilunar ganglion ; 

 the lesser splanchnic hkewise sends most of its branches to that 

 ganglion, but it also transmits two or three long filaments back- 

 ward to the renal plexus : and both the splanchnics detach com- 

 municating filaments to the sympathetic. 



The semilunar ganglioti, consequently, is constituted of 

 branches from the left division of the par vagum, and of almost 

 all those of the splanchnic divisions of the sympathetic. This 

 ganglion partakes of the semilunar figure, lies close underneath 

 the posterior aorta, at the root of the coeliac artery, and occu- 

 pies the space between that vessel and the anterior mesenteric 

 artery. It consists of a number of small ganglia, connected one 

 to another, and is surrounded by a plexus of nervous filaments; 

 which little ganglia have been denominated the caliac. From 

 the irregular convex border of the semilunar ganglion, nervous 

 filaments shoot in various directions, and these, from having 

 been likened to the rays of the sun, have been denominated, 

 altogether, the solar plexus ; from which divergent filaments 

 the several minor plexuses of the abdomen may be said to derive 

 their formation, taking names according to the viscera they are 

 particularly designed to furnish with nerves. The fiist to be 

 noticed is 



The splenic plexus — a network of small nerves surrounding the 

 splenic artery. It sends some filaments to the pancreas, but the 

 majority of its detachments run to the spleen. 



The hepatic plexus consists of a similar nervous interlacement 

 around the hepatic artery : it is very extensive ; for it winds 

 round the vessel from its origin to its termination in the porta 

 of the liver. It transmits filaments — 1. Along with the phrenic 

 arteries to the diaphragm. 2. To the stomach. 3. To the pan- 

 creas. 4. It then divides into right and lej't hepatic plexuses, 

 which cling to the arteries of the same names, and accompany 

 them in their ramifications through the liver. 



The anterior mesenteric plexus includes a vast assemblage of 

 nervous filaments intricately wound round the trunks of the 

 anterior mesenteric arteries, and furnishing numerous filaments 

 that proceed along with these vessels, greatly exceeding them in 

 number, to ramify within the substance of the small intestines, 

 ccecum, and coecal portion of the colon. 



The aortic plexus is a name given to the frequent intercommu- 

 nication of some fine filaments sent backward along the posterior 



