SOLAR PLEXUS 835 



The fibres which pass to the cardiac plexuses are medullated and iion-medullated; 

 the former are inhit)itory. the hitter motor. The inhil)it()ry fibres leave the central 

 nervous system Ijy the spinal accessory and vagus nerves, the motor fibres Ijy the 

 roots of the dorsal nerves. 



SOLAR PLEXUS 



The solar plexus is placed in front of the commencement of the abdominal 

 aorta. It is the largest of tlie prevertebral plexuses, and is formed by the two 

 semilunar ganglia, and by a number of interlacing nerve-cords Avhich surround the 

 ganglia. Each semilunar ganglion is placed at the side of the coeliac axis, embrac- 

 ing the artery in its concavity. The upper and the lower extremities of the ganglia 

 of oj)posite sides are connected to one another l)y nerve-cords, above and below the 

 artery. In this manner the cceliac axis is surrounded by a neuro-ganglionic collar. 

 From this neuro-ganglionic collar a numlxn* of branches arise which are joined by 

 branches from the right vagus and Ijy both small sitlanchnic nerves, and in this 

 manner the solar plexus is formed. From the solar plexus a number of nerves 

 arise which accom])any the abdominal aorta and its branches, forming secondary 

 plexuses, which take their names from the arteries they accompany. 



Semilunar ganglia. — These are a pair of reddish-grey, irregularly sha]»ed 

 bodies whicli rest ou the crura of the diaphragm, close to the ea4iac axis. The 

 great sjjlanchnic nerve on each side, after piercing the crus of the diaphragm, 

 enters the outer, or convex, side of the corresponding ganglion. 



Cceliac plexus. — The celiac plexus surrounds the coeliac axis, and divides into 

 splenic, hepatic and coronary plexu.ses. 



The splenic plexus, after receiving a communication from the right pneumo- 

 gastrie nerve, accompanies the splenic artery to the sjileen. It gives ofif j^ancreatic 

 and left gastro-epiploic plexuses. 



The hepatic plexus is joined, near the pyloric end of the stomach, by branches 

 from tlie left imeumogastric. and accompanies the hepatic artery to the liver, where 

 it divides into right and left liepatic plexuses. Previous to its ili vision, it gives off 

 pyloric, right gastro-epiploic, and pancreatico-duodenal plexuses. From the 

 right hepatic plexus a cystic i»lexus is furnished to the gall-bladder. 



The coronary plexus follows the lesser curvature of the stomach, pi'oceeding 

 from left to right. In this course it is joined by ])ranches from the left pneumo- 

 gastric, and. after giving off numerous twigs to the stomach, ends, near the pylorus. 

 by joining the pyloric plexus. 



The diaphragmatic plexuses arise from the upper extremities of the semilunar 

 ganglia, and accompany tlie diai)hragmatic arteries to the under surface of the 

 dia|)hragm. On the rii:ht side a eoniiiiunication is efTected Avith the phrenic nerve, 

 a small ganglion (ganglion diaphragmaticum ) being formed at the point of com- 

 munication. 



The suprarenal plexuses are derived, in part from the diaitlu-agmatic. in i)art 

 from the solar, and in ])art from the renal ])lexuses; they are distributed chiefiy to 

 the medullary portions of the suprarenal liodies. 



The renal plexuses are formed by branches of the solar and aortic plexuses, 

 and are joined })Osteriorly by the smallest splanchnic nerves. Each renal ]^lexus 

 surrounds the corresponding renal artery; it contains groups of ganglion cells and 

 enters the hiluni of the kidney, where it subdivides in the fatty tissue whieli occu- 

 pies the sinus, and enters the substance of the kidney with the V)lood-vessels. 



The superior mesenteric plexus is <if large size, and is remarkal)le for the 

 comparatively white eolovu- of the nerves whicli com]>ose it. It is derived from 

 the solar plexus, anil, after emerging from under cover of the jiancreas. closely 

 surrounds the trunk of the su]>erior mesenteric artery. In this situation a few 

 ganglia (ganglia mesenterica) are formed. Having given off branches, which 

 accompany the coliea media, colica dextra, and ileocolic arteries, the greater jiart 

 of the plexus enters the mesentery, where the nerv'es — no longer closely following 

 the blood-vessels, spread out lietween the layers of the mesentery, and eventually 

 reach the small intestine. 



The aortic plexus is in the form of two vast networks of nerves whicli are 



