THE NERVOUS SYSTEM 377 



It then proceeds to the side of the aorta between the cceliac axis and 

 the large mesenteric artery, where it has upon it the semilunar or solar 

 ganglion. This is a body of considerable size and importance. It is joined 

 to its fellow on the opposite side by a large wide branch and numerous 

 smaller ones, resulting in the formation of a plexus beneath the aorta 

 termed the solar j^lexus. 



After receiving some branches from the pneumogastric nerve, this 

 plexus splits up into several smaller plexuses, which form a net-work round 

 the arteries, and through them the sympathetic is distributed to the several 

 al)dominal organs. In this way we get the gastric plexus to the stomach, 

 the hepatic plexus to the liver, duodenum, pylorus, and pancreas, a splenic 

 plexus to the spleen, and also a plexus to the stomach. A large plexus, 

 the anterior mesenteric, surrounds the artery of that name, and is dis- 

 tributed over the organs supplied by it. A renal plexus encircles the 

 renal artery and accompanies it to the kidney. 



The lumbo-aortic plexus passes backward along the under surface of 

 the aorta, and mixes its fibres with the posterior mesenteric plexus. 



The great splanchnic nerve leaves the dorsal chain about the 

 seventh intercostal space. From this point it receives a few afferent fibres 

 from the ganglia, commencing with the sixth, and continues to do so irregu- 

 larly up to the sixteenth. Behind, the gi'eat splanchnic ends in the solar 

 plexus. 



The lesser splanchnic nerve is made up of two or three small 

 branches proceeding from the last dorsal ganglion; these collect into a 

 short thin branch, which joins the solar plexus or the renal and supra- 

 renal plexuses. 



Lumbar Sympathetic. — This is a continuation of the dorsal sym- 

 pathetic, and has upon it ganglia corresponding to the number of lumbar 

 nerves from the inferior division of which it receives its afferent branches. 

 Behind, it is continued by the sacral sympathetic. 



Its efferent branches consist of short filaments to the lumbo-aortic 

 plexus. The small mesenteric artery receives others, which surround the 

 vessel and form the posterior mesenteric plexus, in the centre of which 

 is a ganglion of some size. This ganglion supplies in addition branches 

 to the posterior mesenteric vein, and others to the spermatic arteries and 

 the rectum. 



Two or three long divisions from each side pass beneath the peritoneum, 

 and on reaching the lateral part of the rectum blend with others from the 

 inferior sacral nerves, forming the plexus from which all the pelvic organs 

 are supplied. 



Sacral Sympathetic. — This region is supplied by a continuation 



