1366 HUMAN ANATOMY. 



which, as well as from the nerve itself, are given off filaments for the supply of the 

 oesophagus, the thoracic aorta and the vertebrae. Sometimes in the thorax it is 

 divided and forms a plexus with the small splanchnic and in this event several small 

 ganglia are present. This nerve consists mainly (four-fifths, according to Riidinger) 

 of medullated fibres, which are direct continuations of white rami from as far up as 

 the third thoracic nerve or even higher. 



The small splanchnic nerve (n. splanchnicus minor) arises from the ninth and 

 tenth, or tenth and eleventh ganglia or from adjacent portions of interganglionic cords. 

 Entering the abdomen by piercing the crus of the diaphragm either in association with 

 or in close proximity to the great splanchnic, it terminates in that portion of the semi- 

 lunar ganglion called the aortico-7'enal ganglion. 



The least splanchnic nerve (n. splanchnicus imus) arises from the lowest of 

 the thoracic ganglia and may receive a filament from the small splanchnic, from which 

 it occasionally takes origin. Piercing the diaphragm in company with the gangli- 

 ated cord it terminates in the renal plexus. 



A fourth splanchnic nerve is rarely present. It is described by Wrisberg as 

 having been found in eight cadavers out of a large number examined. It is formed 

 by filaments from the cardiac nerves, aided by twigs from the lower cervical and 

 upper thoracic ganglia. 



THE LUMBAR PORTION OF THE GANGLIATED CORD. 



The lumbar portion of the gangliated cord (pars abdominalis systematis sympa- 

 thetici) (Fig. 1 134) consists usually of four small oval ganglia connected by association 

 cords. There may be a decided increase in the number of the ganglia, as many as 

 eight having been found, and, on the other hand, occasionally there are fewer than 

 four, there being under these circumstances a compensatory increase in the size of the 

 ganglia present. The lumbar portion of the sympathetic lies nearer the median line 

 than does the thoracic, the cords being placed anterior to the bodies of the lumbar 

 vertebrae and the lumbar vessels, along the mesial border of the psoas magnus, on 

 the left side being partially concealed by the aorta and on the right by the inferior 

 vena cava. It is connected w;ith the thoracic portion by a small association cord, 

 which passes either through or posterior to the diaphragm, and with the sacral portion 

 by a cord which descends behind the common iliac artery. White rami communi- 

 cantes are received from the first, the second and sometimes the third lumbar nerve, 

 additional white fibres being derived from the lower thoracic nerves by way of the 

 gangliated cord. 



The somatic branches comprise the peripheral distribution of the gray rami 

 commu7iicayites. These are the longest to be found in the body, on account of the 

 distance between the ganglia and the intervertebral foramina. They accompany the 

 lumbar vessels and pass beneath the fibrous arches from which the psoas magnus 

 takes origin. 



1. The white rami communicantes are derived from the upper two or 

 three lumbar nerves and join the upper ganglia or the adjacent portion of the inter- 

 ganglionic cord. They contain splanchnic efferent and afferent fibres, which continue 

 downward the distribution of the thoracic portion of the gangliated cord, including 

 vasomotor and secretory fibres for the lower extremities, pilomotor fibres, vaso- 

 motor fibres for the abdominal vessels, motor fibres for the circular musculature 

 of the rectum and inhibitory fibres for the longitudinal muscle of the rectum. Fibres 

 peculiar to the lumbar region include vasomotor nerves of the penis and motor fibres 

 for the bladder and uterus, those to the bladder supplying the sphincter as well 

 as the circular and longitudinal muscle-fibres, those to the last-mentioned group 

 being inhibitory. 



2. The gray rami communicantes are irregular in number and arrange- 

 ment, sometimes a single one dividing and joining two lumbar nerves and sometimes 

 two to five passing to a single spinal nerve. 



The visceral branches vary considerably in their distribution, some joining 

 the hypogastric plexus (plexus hypogastricus), others the aortic plexus (plexus aorticus 

 abdominalis) and still others supplying the vertebrae and their ligaments. 



