1074 



THE NERVE SYSTEM 



the costal pleura; the last two ganglia are, however, anterior to the rest, being 

 placed on the side of the bodies of the eleventh and twelfth thoracic vertebrae. The 

 ganglia are small in size and of a grayish color. The first ganglion, larger than 

 the others, is of an elongated form and is frequently blended with the last cervical 

 ganglion. They are connected by the intervening portions of the cord. 



Two rami communicantes, one white and the other gray, connect each ganglion 

 with its corresponding spinal nerve. 



The branches from the upper five ganglia are very small; they supply filaments 

 to the thoracic aorta and its branches, and to the bodies of the vertebrae and their 

 ligaments. Branches from the second, third, and fourth ganglia enter the posterior 

 pulmonary plexus. 



The branches from the lower seven ganglia are large, and white in color; they 

 distribute filaments to the aorta, and unite to form the three splanchnic nerves. 

 These are named the great, the lesser, and the smallest, or renal splanchnic. 



The great splanchnic nerve (n. splanchnicus major} is white in color, firm in 

 texture, and is formed by branches from the thoracic ganglia between the fifth or 

 sixth and the ninth or tenth; but the fibres in the higher roots may be traced 

 upward in the sympathetic cord as far as the first or second thoracic ganglion. 

 These roots unite to form a cord of considerable size. It descends obliquely 

 inward in front of the bodies of the vertebra? along the posterior mediastinum, 

 perforates the cms of the Diaphragm, and terminates in the semilunar ganglion of 

 the solar plexus (Fig. 784), distributing filaments to the renal and suprarenal 

 plexuses. A ganglion (ganglion splanchnicum) exists on this nerve opposite the 

 eleventh or twelfth thoracic vertebra. 



The lesser splanchnic nerve (n. splanchnicus minor) is formed by filaments from 

 the tenth and eleventh ganglia, and from the cord between them. It pierces the 

 Diaphragm near or with the preceding nerve, and joins the aorticorenal ganglion 

 of the solar plexus (Fig. 784). It communicates in the thorax with the great 

 splanchnic nerve, and ends in the solar plexus. 



The least splanchnic nerve (n. splanchnicus imus~) arises from the last thoracic 

 ganglion, and, piercing the Diaphragm, terminates in the renal plexus. It occa- 

 sionally communicates with the preceding nerve. 



A striking analogy appears to exist between the splanchnic and the cardiac 

 nerves. The cardiac nerves are three in number, they arise from the three cer- 

 vical ganglia, and are distributed to a large and important organ in the thoracic 

 cavity. The splanchnic nerves, also three in number, are connected probably 

 with all the thoracic ganglia, and are distributed to important organs in the 

 abdominal cavity. 



The Lumbar Portion (Pars Lumbalis) of the Gangliated Cord (Fig. 780). 



The lumbar portion of the gangliated cord is situated in front of the vertebral 

 column along the inner margin of the Psoas magnus. It consists usually of four 

 ganglia, connected together by interganglionic cords. It is continuous above with 

 the thoracic portion beneath the internal arcuate ligament of the Diaphragm, 

 and below with the sacral portion behind the common iliac artery. The ganglia 

 are of small size, and placed much nearer the median line than the thoracic ganglia. 



Gray rami communicantes connect all the ganglia with the lumbar spinal 

 nerves. There may be two from each ganglion, but the arrangement is not so 

 uniform as in other regions. The first and second, and sometimes the third, 

 lumbar nerves send white rami communicantes to the upper two or three ganglia. 



From the situation of the lumbar ganglia these branches are longer than in the 

 other regions. They accompany the lumbar arteries around the sides of the bodies 



