GENERAL ARRANGEMENT OF THE SYMPATHETIC SYSTEM. 639 



pneumogastric and the glosso-pharyngeal to form the pharyngeal plexus, and 

 branches which form a plexus on the external carotid, the vertebral and the 

 thyroid arteries, following the ramifications of these vessels. 



From the cervical portion of the sympathetic the three cardiac nerves 

 arise and pass to the heart, entering into the formation of the cardiac plexus. 

 The superior cardiac nerve arises from the superior ganglion ; the middle 

 nerve, the largest of the three, arises from the middle ganglion or from the 

 sympathetic cord, when this ganglion is wanting; and the inferior nerve 

 arises from the inferior cervical ganglion or the first thoracic. These nerves 

 present frequent communications with various of the adjacent cerebro-spinal 

 nerves, penetrate the thorax, and form the deep and superficial cardiac plex- 

 uses and the posterior and the anterior coronary plexuses. In these various 

 plexuses, there are found ganglioform enlargements ; and upon the surface 

 and in the substance of the heart, are collections of nerve-cells connected 

 with the fibres. 



Thoracic Ganglia. The thoracic ganglia are situated in the chest, be- 

 neath the pleura, and rest on the heads of the ribs. They are usually twelve 

 in number, but occasionally two are fused into one. They are connected to- 

 gether by the sympathetic cord. They each communicate by two filaments 

 with the cerebro-spinal nerves. One of these is white, like the spinal nerves, 

 and probably passes to the sympathetic, and the other, of a grayish color, is 

 thought to contain the true sympathetic filaments. From the upper six gan- 

 glia filaments pass to the aorta and its branches. The branches which form 

 the posterior pulmonary plexus arise from the third and fourth ganglia. 

 The great splanchnic nerve arises mainly from the seventh, eighth and ninth 

 ganglia, receiving a few filaments from the upper six ganglia. This is a large, 

 white, rounded cord, which penetrates the diaphragm and passes to the semi-" 

 lunar ganglion, sending a few filaments to the renal plexus and the suprare- 

 nal capsules. The lesser splanchnic nerve arises from the tenth and eleventh 

 ganglia, passes into the abdomen and joins the cceliac plexus. The renal 

 splanchnic nerve arises from the last thoracic ganglion and passes to the re- 

 nal plexus. The three splanchnic nerves present frequent anastomoses with 

 each other. 



Ganglia in the Abdominal and the Pelvic Cavity. The semilunar gan- 

 glia on the two sides send off radiating branches' to form the solar plexus., 

 They are situated by the side of the cceliac axis and near the suprarenal capsules. 

 These are the largest of the sympathetic ganglia. From these arise plexuses 

 distributed to various parts in the abdomen, as follows : The phrenic plexus 

 follows the phrenic artery and its branches to the diaphragm. The coeliac 

 plexus subdivides into the gastric, hepatic and splenic plexuses, which are 

 distributed to organs, as their names indicate. From the solar plexus differ- 

 ent plexuses are given off, which pass to the kidneys, the suprarenal capsules, 

 the testes in the male and the ovaries in the female, the intestines (by the 

 superior and inferior mesenteric plexuses), the upper part of the rectum, the 

 abdominal aorta and the vena cava. The filaments follow the distribution of 

 the blood-vessels in the solid viscera. 



