THE PREVERTEBRAL PLEXUSES 1011 



Construction of the lumbar and sacral portions of the sympathetic trunk. 



The ganglia of both these portions of tin- In ink an -very variable in shape, size, position, 

 andnumber. There are usually four ganglia belonging to ea< h port ion. hut soniet lines 

 as many as eight may he distinguished in the lumhar or there may he as many as six 

 in the sacral portion. In the majority of cases, especially in the sacral region, these 

 masses of culls are so fused that their numher is less than the numher of the spinal 

 nerves with which they are associated. As noted above, only the first two or three 

 lumbar spinal nerves send white mini which connect as such directly with these 

 ganglia. However, splanchnic efferent fibres descend this entire stretch of the 

 trunk, through both the lumbar and sacral portions, from the white rami of the 

 lower thoracic and the upper lumhar nerves above. These fibres either terminate in 

 the various ganglia or pass uninterrupted into the peripheral branches, and are con- 

 cerned in the transmission of impulses which are vaso-motor to the genital organs, 

 motor for the uterus, the vas deferens, and the circular coat of the bladder. Also, 

 some of them convey secretory, pilo-motor, and vaso-motor impulses for the glands, 

 skin, and vessels of the lower extremity in addition to the similar impulses conveyed 

 in the peripheral branches from the lower part of the thoracic portion of the sympathetic 

 trunk. The motor fibres for the uterus or vas deferens and for the bladder pass, 

 in most part probably, by way of the peripheral branches from the lumbar portion 

 of the cord, through the aortic plexus to the inferior mesenteric ganglion; others, 

 the vaso-motor fibres to the genital organs especially, pass by way of the sacral gan- 

 glia and the peripheral branches from them to the hypogastric or pel vie plexus and the 

 appropriate sub-plexuses of this region. Of the vaso-motor fibres for the penis, some 

 of the constrictor fibres pass down the sacral portion of the sympathetic trunk and 

 terminate about the cells of the sacral ganglia, and these cells send out sympathetic 

 fibres which join and course in the pudic nerve (n. pudendus). 



All of both the lumbar and sacral spinal nerves receive grey rami from the sympa- 

 thetic trunk. These, just as those from the other portions of the trunk, consist of 

 (1) vaso-motor fibres to the meninges and vessels of the vertebral canal; (2) sympa- 

 thetic fibres which join the divisions of the spinal nerves and course in them to their 

 distribution, and (3) afferent sympathetic fibres terminating in the spinal ganglia. 



In addition to the efferent splanchnic fibres, the branches of the lumbo-sacral por- 

 tion of the sympathetic trunk carry cerebro-spinal fibres of general sensibility- 

 sensory fibres arising in the spinal ganglia of this and the lower thoracic region. 



There are no white rami proper passing from the sacral spinal nerves to course or 

 terminate in the sympathetic trunk. Efferent splanchnic fibres are given off by these 

 nerves in abundance, but, instead of entering the trunk and its ganglia, they form 

 bundles which pass over the trunk and directly into its peripheral branches. The 

 bundles passing from the second, third, and fourth sacral nerves are large and 

 especially definite. While homologous to white rami, such bundles are better 

 known as the visceral branches of the sacral nerves or the pelvic splanchnics. 

 They contain some cerebro-spinal sensory fibres (afferent splanchnic), but consist 

 for the most part of efferent splanchnic fibres, conveying impulses, vaso-motor 

 (vaso-dilator, chiefly) to the genital organs, both motor and inhibitory for the rec- 

 tum, uterus, and bladder (longitudinal coat especially), and secretory for the pros- 

 tate gland. These fibres contribute to the hypogastric plexus and are interrupted 

 in the small ganglia of its sub-plexuses, named according to the various urino-genital 

 organs concerned. 



THE GREAT PREVERTEBRAL PLEXUSES 



The great prevertebral plexuses are three in number, the cardiac, the cceliac 

 (solar or epigastric), and the hypogastric or pelvic. The cardiac plexus lies behind and 

 below the arch of the aorta, and the cceliac and hypogastric plexuses are situated in 

 front of the lumbar vertebrae. Each plexus receives not only sympathetic fibres 

 which have passed from or through the ganglia of the sympathetic trunks of either 

 side, but also both afferent and efferent cerebro-spinal nerve-fibres derived directly 

 from the cerebro-spinal nerves. In addition the cardiac and co>liac plexuses receive 

 both efferent splanchnic and cerebro-spinal sensor}' or afferent splanchnic fibres 

 from both vagus nerves. It should be clearly understood that the branches which 

 run from the sympathetic trunks to the prevertebral plexuses contain medullated 



