! 



1032 THE NERVOUS SYSTEM 



vagus, and spinal accessory nerves, all of which have more or less irregularly disposed com- 

 municating rami. The gangUa of origin of the vagus, more than perhaps any other nerve, both 

 receive impulses from visceral efferent fibres and give origin to sympathetic fibres. Likewise 

 twigs of other cranial nerves, especially of the trigeminus, connect with (pass through) the small 

 sympathetic ganglia of the head. The meningeal branches given by certain of the cranial nerves 

 contain vaso-motor fibres, and these correspond to the sympathetic fibres in the recurrent 

 branches and in the roots of the spinal nerves. 



It is known that spinal ganglia and certain of the ganglia of the cranial nerves 

 contain cell-bodies of sympathetic neurones — cell-bodies which, during the period 

 of the migration peripheralward, remained within the confines of these ganglia 

 (fig. 785). These cell bodies receive efferent impulses from ventral root fibres 

 and send their axones fm-ther into the periphery just as if in the sympathetic 

 ganglion. Their relative abundance is not known. It is supposed that the ganglia 

 of the vagus, glosso-pharyngeus, trigeminus and the geniculate ganglion contain 

 a considerable proportion of such sympathetic cell-bodies. 



From the above it may be seen that the ganglia and connecting trunks and rami 

 of the S3'mpathetic system may be divided as follows: — (1) The two sympathetic 

 gangliated trunks lying proximal to and parallel with the vertebral column; (2) the 

 great prevertebral plexuses, of which there are roughly four, one in the head, one 

 in the thorax, one in the abdomen, and one in the pelvic cavity (fig. 784), each of 

 which is subdivided; (3) the numerous terminal ganglia and plexuses situated 

 either within or close to the walls of the various organs; (4) the trunks and rami 

 associating the ganglia with each other and thus contributing to the plexuses, or 

 connecting the ganglia with other nerves or with the organs with whose innerva- 

 tion they are concerned. The trunks and rami may be divided into — (a) the 

 rami communicantes, or central branches, connecting the sympathetic with the 

 cranio-spinal and central systems; (6) associative trunks, best considered as those 

 which associate sympathetic ganglia situated on the same side of the body; (c) 

 commissural branches, or those which associate ganglia situated on opposite sides 

 of the mid-line of the body, such as the transverse connecting branches between 

 the sympathetic trunk in the lumbo-sacral region (fig. 787), or all the associating 

 trunks between the ganglia of plexuses occupying the mid-region of the body; 

 (d) terminal or peripheral branches, or those which pass from the ganglia to their 

 final distribution apparently uninterrupted by other ganglia. 



THE SYMPATHETIC TRUNKS 



The sympathetic gangliated trunks, or gangliated cords, of the sympathetic 

 system are two symmetrical trunks with ganglia interposed in them at intervals 

 of varying regularity, and extending vertically, one on each side of the ventral 

 aspect of the vertebral column, from the second cervical vertebra to the first 

 piece of the coccyx. Upon the coccyx the two trunks unite and terminate in a 

 single medial ganglion, the ganglion coccygeum impar. The various ganglia are 

 connected with the cranio-spinal nerves by the rami communicantes. Mor- 

 phologically, each trunk might be expected to possess thirty-one ganglia, one for 

 each spinal nerve, but, owing to the fusion of adjacent ganglia in certain regions, 

 especially in the cervical, there are in the adult only twenty-one or twenty-two 

 ganglia in each trunk. These occur as thi'ee cervical ganglia, ten or eleven thoracic 

 ganglia, four lumbar and jour sacral ganglia, and the ganglion coccygeum impar, 

 which is common to both trunks. 



In the cervical region the sympathetic trunks lie in front of the transverse processes of the 

 vertebra;, from which they are separated by the longus capitis (rectus capitis anticus major) 

 and longus colli; in the thoracic region they lie at the sides of the bodies of the vertebra; and on 

 the heads of the ribs; in the lumbar region they are placed more vcntrally with reference to 

 the spinal nerves and more in front of the bodies of tlie vertebra; and along the anterior borders 

 of the psoas muscles; in the pelvis the ganglia lie between and ventral to the openings of the 

 sacral foramina. In the lower lumbar and sacral region one ganglion may send rami commu- 

 nicantes to two spinal nerves and one spinal nerve may be connected with two ganglia. The 

 ganglia of the trunks throughout give off a-s.sociative branches to the ganglia of the prevertebral 

 plexu-ses and branches to the nearby vi.scera and blood-vessels. These branches may appear 

 either white or grey according to the jMcdoininance of medullated or non-niedullated fibres in 

 them. In the lumbo-sacral region coiiirnissural or transverse branches between the ganglia 

 of the two trunks are especially abundant. Jn trunks having a whiter appearance, the greater 

 part of tli(! medullated fibres producing it an; sensory and visceral motor fibres from the spinal 

 nerves which have passed through the sympathetic ganglia without termination. The nerve 

 trunks connecting the ganglia of the sympathetic trunks all contain three varieties of fibres: — (1) 



