NEUROLOGY. 141 



angular, the base towards the spine, the apex external, covered by tho. 

 pleura and a thin fascia. All communicate by their external branches with 

 the anterior or intercostal branches of the spinal nerves. From the base or 

 anterior edge of each ganglion, arise the internal branches, the mediastinal, 

 and the great and lesser splanchnic. 



The great splarichnic nerve arises by four or five distinct roots from the 

 sixth, seventh, eighth, ninth, and tenth ganglions ; they descend forwards 

 and unite into a long, flat cord which enters the abdomen, where each 

 nerve expands into the semilunar ganglion. The real origin of this nerve 

 is from the cerebro-spinal system. 



The lesser sj^lanclmic nerve arises by two roots fi'om the tenth and 

 eleventh ganglions, Avhich unite on the side of the last dorsal vertebra. 

 The small nerve tlms constituted enters the abdomen through the crus of 

 the diaphragm, and then ends in the renal plexus. 



The semilunar ganglion of each side is situated on the diaphragm, and 

 ]iartly on the aorta, on either side of the cosliac axis, and above and behind 

 the supra-renal capsule. These are the largest ganglions on the sympa- 

 thetic ; though called sejui-lunar, their form is very variable and irregular. 

 and fre(iuently instead of a single mass they consist of a congeries of knot- 

 ted ganglions on the nervous cord ; the right and left communicate with 

 each other by several filaments, on which again small ganglions are placed. 

 This communication suiTounds the coeliac axis, and, as branches radiate 

 from it in all directions, it is termed the solar plexus. This plexus is 

 situated in the epigastrium, behind the stomach, in front of the aorta, and 

 above the pancreas. In this })lexus there are also some filaments from the 

 lesser splanchnic and phrenic nerves, and the right vagus terminates in it ; 

 it is the most highly developed portion of the sympathetics, and has been 

 regarded as the head or centre of the great organic nervous system bv 

 some, who maintain the independence of the ganglionic system and its dis- 

 tinctness from the cerebro-spinal nerves. From it numerous nerves pass 

 off in various directions ; these nerves accompany the blood-vessels, and 

 form plexuses around each, which are named, according to their destination, 

 hepatic, splanchnic^ gastric^ &c. 



1. The phrenic plexuses consist of branches arising on each side from 

 the upper part of the solar plexus, accompany the phrenic arteries, and 

 enter the diaphragm beneath tlie peritonaeum ; some branches follow the 

 phrenic vessels, others jDass in different directions, and join some minute 

 filaments from the phrenic nerves of the cervical plexus. 



2. The supra- renal plexuses arise partly from the last, and, l)y some deli- 

 cate filaments from the semilunar ganglion of each side, they twine around 

 the arteries which conduct them into the supra-renal bodies. 



8. The coronary or gastric plexus. This fesciculus arises from the upper 

 and anterior part of the solar and from the right \ agus, and accompanies 

 the arteria coronaria ventriculi, along the lesser curvature of the stomach, 

 to the lesser omentum ; its filaments are lost in the submucous tissue, and 

 communicate with those of the right and left vagi. 



■i. The hepatic plexus is a very large fasciculus, arising partly from the 



847 



