GENERAL ARRANGEMENT OF THE SYMPATHETIC SYSTEM. 733 



and the seventh cervical vertebrae respectively. The middle ganglion is sometimes want- 

 ing, and the inferior is occasionally fused with the first thoracic ganglion. These ganglia 

 are connected together by the so-called sympathetic cord. They have numerous fila- 

 ments of communication above, with the cranial and the cervical nerves of the cerebro- 

 spinal system. Branches from the superior ganglion go to the internal carotid, to form 

 the carotid and the cavernous plexus, following the vessels as they branch to their dis- 

 tribution. Branches from this ganglion pass to the cranial ganglia. There are also 

 branches which unite with filaments from the 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 artery, 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 cardiao 

 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 want- 

 ing; and the inferior nerve arises from the inferior cervical ganglion or the first thoracic. 

 These nerves present numerous communications with various of the adjacent cerebro- 

 spinal nerves, penetrate the thorax, and form the deep and the superficial cardiac plexus 

 and the posterior and the anterior coronary plexus. In these various plexuses, are found 

 numerous ganglioform enlargements ; and, upon the surface and in the substance of the 

 heart, are numerous collections of nerve-cells connected with the fibres. 



Thoracic Ganglia. The thoracic ganglia are situated in the chest, beneath 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 together 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 ganglia, 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 semilunar ganglion, sending a few filaments to the renal 

 plexus and the suprarenal capsules. The lesser splanchnic nerve arises from the tenth 

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

 splanchnic nerve arises from the last thoracic ganglion and passes to the renal plexus. 

 The three splanchnic nerves present numerous anastomoses with each other. 



Ganglia in the Abdominal and the Pelvic Cavity. The semilunar ganglia 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 sym- 

 pathetic ganglia. From these arise numerous plexuses distributed to various parts in 

 the abdomen, as follows : The phrenic plexus follows the phrenic artery and its branches 

 to the diaphragm. 'The cceliac plexus subdivides into the gastric, hepatic, and splenic 

 plexuses, which are distributed to organs as their names indicate. From the solar pi. 

 different 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 the 

 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. 



The lumbar ganglia, four in number, are situated in the lumbar reirion, upon the 

 bodies of the vertebra. They are connected with the pnnglia above and below and with 

 each other by the sympathetic cord, receiving, like the other pmirlin, filaments from the 

 spinal nerves. Their branches of distribution form the aortic lumbar plexus and the 

 hypogastric plexus and follow the course of the blood-vessels. 



