THE ABDOMINAL AND PELVIC PLEXUSES 713 



of the plexus, on which arc minute gangha, ramify with the bronchi in the substance 

 of the lung/ The oesophageal branches join with those of the vagus in the forma- 

 tion of the oesophageal plexus (P. oesophageus) . 



The great splanchnic nerve (N. splanchnicus major) arises by a series of roots 

 derived from the sixth or seventh to the fifteenth or sixteenth thoracic ganglia 

 inclusive. It extends at first along the inner side of the thoracic trunk, then crosses 

 the latter ventrally, passes back between the crus of the diaphragm and the outer 

 border of the psoas minor, and joins the cceliac ganglion. It is small at its origin, 

 but becomes considerably larger than the sympathetic trunk. Near its termination 

 it bears the small splanchnic ganglion, from which and from the nerve, filaments go 

 to the aorta, the a^sophagus, and the vertebra?. 



The small splanchnic nerve (N. splanchnicus minor) is formed by roots derived 

 from the last two or three thoracic ganglia. It runs back with the great splanchnic 

 nerve, but ends in the cceliac or in the renal and adrenal plexuses. 



Tliis nerve is not always present and is variable in arrangement. The roots communicate 

 by filaments with the great splanchnic. 



4. The abdominal part of the sympathetic trunk (Pars abdominalis systematis 

 sympathici) lies along the inner border of the psoas minor, above the aorta on the 

 left side and the posterior vena cava on the right (Fig. 524) . The trunk is smaller 

 than the thoracic part, and presents usually six small fusiform lumbar ganglia (G. 

 lumbalia), which are connected by rami communicantes with the ventral divisions 

 of the lumbar nerves. Visceral branches go to the aortic and hypogastric plexuses, 

 and to the cceliac and mesenteric ganglia. 



5. The pelvic part of the sympathetic trunk (Pars pelvina systematis sympa- 

 thici) begins at the last lumbar ganglion and extends along the pelvic surface of 

 the sacrum internal to the emergence of the ventral branches of the sacral nerves 

 (Fig. 451). At the third segment of the sacrum the trunk divides into internal 

 and external branches. The internal branch inclines to the median plane and 

 unites with the opposite branch. At the junction there is often found the small 

 coccygeal ganglion (G. impar), which lies on the coccygeal artery at the joint 

 between the first and second coccygeal vertebrae. A filament from the ganglion 

 accompanies the artery. The external branch communicates with the last two 

 sacral nerves and joins the ventral coccygeal nerves. Ganglia occur near each of 

 the first three sacral foramina, and are connected by gra}' rami communicantes 

 with the adjacent spinal nerves. The visceral branches are distributed through the 

 hypogastric plexus. They supply motor fibers to the longitudinal and inhibitory 

 fibers to the circular muscular coat of the rectum, motor fibers to the bladder and 

 uterus, and the vaso-dilator fibers (Nn. erigentes) to the penis. 



THE ABDOMINAL AND PELVIC PLEXUSES 



The chief plexuses which distribute nerves to the viscera and vessels of the 

 abdominal and pelvic cavities are two in number, the solar and the pelvic. From 

 them fibers proceed to form numerous subsidiary plexuses which are named accord- 

 ing to the organs which they supply or the vessels which they enlace. 



The Solar Plexus 

 The solar plexus (Fig. 450) is situated on the dorsal wall of the abdominal 

 cavity in relation to the aorta and the origin of its chief visceral branches. It com- 

 prises the cceliaco-mesenteric ganglia and the cceliac and anterior mesenteric 

 plexuses. 



' The right and left plexuses communicate with each other, so that both lungs receive fibers 

 from both vagi. 



