892 THE NERVES. 



a. Great splanchnk nervps (Fig. 480, 7). — This commences to be detached 

 from the doreal chain towards the sixth or seventh ganglion, is directed backwards 

 bj 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 above and 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 plexas, receives some branches from the superior 

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

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

 network : the ramifications of this— 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 the parietes of which its branches anastomose with those of the 

 pneimiogastrics. 2. A hepatic plexus, for 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 

 supra-renal plexus — double, and scarcely distinct from each other — send their 

 terminal divisions to the kidneys and supra-renal capsules. The terminations of 

 the filaments of these plexuses have been already described in the Splanchnology. 



It is necessary to add to this rich nervous apparatus, the lumbo-aorfic plextis, 

 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. 



h. Lesser splanchnic nerve (Fig. 480, 8). — This branch is composed of two 

 or three filaments that emanate from the last subdorsal ganglia, and which, 

 instead of joining the great splanchnic nerve like the others, with which they 

 communicate by one or two fine divisions, collect in a short thin cord, the rami- 

 fications of which pass directly into the solar plexus, or are confounded with the 

 nerves of the kidney and the supra-renal capsule. 



4. Lumbar Portion of the Sympathetic. 

 This is a cord similar to that of the dorsal portion, and provided with fusi- 

 form ganglionic enlargements equal in number to the pairs of lumbar nerves. 

 This cord is applied against the psoas parvus, near the common inferior vertebral 

 ligament, and is covered on the left by the aorta, on the right by the posterior 

 vena cava. It is directly continued by the sacral portion of the sympathetic 

 chain, at the lumbo-sacral articulation. 



