THE GREAT SYMPATHETIC NERVOUS SYSTEM. 787 



cavity by the lumbar portion, after passing through the arch of the superior 

 border of the diaphragm, along with the psoas parvus. 



Along its course, this cord exhibits, at each intercostal space, a small 

 fusiform ganglionic enlargement seventeen in all. The two or three first 

 are most frequently absent ; but then the anterior extremity of the nerve 

 has for some extent the appearance of a ribbon-shaped ganglion, which seems 

 to be due to the elongation, posteriorly, of the inferior grey mass of the 

 cervical portion. 



AFFERENT BRANCHES. Furnished by the inferior branches of the dorsal 

 nerves, these ramuscules number from one to three for each ganglion. To 

 proceed from the iutervertebral foramina to the sympathetic, they traverse the 

 superior extremity of the intercostal space, passing sometimes behind, some- 

 times before, the arteries of that name. 



EMERGENT BRANCHES. A very few delicate branches pass to the pleurss ; 

 those which demand notice are the great and lesser splanchnic nerves. 



a. Great splanchnic nerves (Fig. 362, 7). This commences to be 

 detached from the dorsal chain towards the sixth or seventh ganglion, is 

 directed backwards by the external side of that chain, receives an accessory 

 branch from each of the enlargements it passes by. except the last two or 

 three, and enters the abdominal cavity through the arch of the psoas parvus, 

 where it usually looks like a small ganglionic mass ; after which, it is 

 inflected inwards, and terminates on the side of the aorta, between the coeliac 

 and mesenteric trunks, by a second and enormously developed mass the solar 

 ganglion. The two solar, or semilunar ganglia, as they have also been 

 designated, and which are the largest in the body, are elongated from before 

 to behind, and flattened from above to below. They communicate with one 

 another by means of a wide and thick greyish cord, which encircles, 

 posteriorly, the trunk of the great mesenteric artery, and by a multitude of 

 filaments which pass from the left to the right, in front of that vessel. From 

 this arrangement results a single plexus situated at the inferior face of the 

 aorta, between the origin of the two precited arterial trunks. 



This plexus, named the solar, receives some branches from the superior 

 oesophageal cord of the pneumogastric nerve. It subdivides on its periphery 

 into several secondary plexuses, which leave, as from a centre, the principal 

 network, and whose ramifications, very large and numerous, proceed to the 

 neighbouring organs in accompanying the arterial divisions, around which 

 we see them interlacing and anastomosing in a very complicated manner. 

 It is for this reason that there have been described separately : 1, A gastric 

 plexus, going to the stomach, on whose parietes its branches anastomose 

 with those of the pneumogastrics ; 2, A hepatic plexus, destined to the 

 liver, duodenum, pylorus, and pancreas ; 3, A splenic plexus, one part of 

 which passes to the spleen, the other to the stomach; 4, An anterior 

 mesenteric plexus, the most considerable of all, is distributed to the same 

 organs as the artery of that name ; 5, A renal and a suprarenal plexus : the 

 latter two doubled, and scarcely distinct from each other, their terminal 

 divisions arriving at the kidneys and suprarenal capsules. The termination 

 of the filaments of these plexuses has been already described in the Splanch- 

 nology. 



It is necessary to add to this rich nervous apparatus, the lunibo-aortic 

 plexus, formed by the large and numerous branches which spring from the 

 solar plexus behind the great mesenteric artery, creep along the sides and 

 the inferior face of the aorta, frequently anastomose with each other, and 

 reunite at the posterior mesenteric plexus. 



