SEMILUNAK GANGLION SOLAR PLEXUS. 433 



by the pleura costalis. The two first and the last ganglia are 

 usually the largest. 



Their branches are superior, inferior, external and internal. 



The superior and inferior are prolongations of the substance of 

 the ganglia rather than branches ; the former to communicate with 

 the ganglion above, the latter with that below. 



The external branches, two or three in number, communicate with 

 each of the spinal nerves. 



The internal brandies of the five upper ganglia are aortic, and 

 follow the course of the intercostal arteries to that trunk: the 

 branches of the lower ganglia unite to form the two splanchnic 

 nerves. 



The Great splanchnic nerve arises from the sixth dorsal ganglion, 

 and receives branches from the seventh, eighth, ninth, and tenth, 

 which increase it to a nerve of considerable size. It descends in 

 front of the vertebral column, within the posterior mediastinum, 

 pierces the diaphragm immediately to the outer side of each crus, 

 and terminates in the semilunar ganglion. 



The Lesser splanchnic nerve (renal) is formed by filaments from 

 the tenth, eleventh, and sometimes from the twelfth dorsal ganglion. 

 It pierces the diaphragm, and descends to join the renal plexus. 



The Semilunar ganglion is a large, irregular, gangliform body, 

 pierced by numerous openings, and appearing like the aggregation 

 of a number of smaller ganglia, having spaces between them. It is 

 situated by the side of the coeliac axis, and communicates with the 

 ganglion of the opposite side, both above and below that trunk, so 

 as to form a gangliform circle, from which branches pass off in all 

 directions, like rays from a centre. Hence the entire circle has 

 been named the solar plexus. 



The Solar plexus receives the great splanchnic nerves ; part of 

 the lesser splanchnic nerves ; the termination of the right pneumo- 

 gastric nerve ; some branches from the right phrenic nerve ; and 

 sometimes one or two filaments from the left. It gives off nume- 

 rous filaments, which accompany, under the name of plexuses, all 

 the branches given off by the abdominal aorta. Thus, we have 

 derived from the solar plexus the 



Phrenic plexuses, 

 Gastric plexus, 

 Hepatic plexus, 

 Splenic plexus, 

 Supra-renal plexuses, 

 Renal plexuses, 

 Superior mesenteric plexus, 

 Spermatic plexuses, 

 Inferior mesenteric plexus. 



The Renal plexus is formed chiefly by the lesser splanchnic nerve, 

 but receives many filaments from the solar plexus. 



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