THE SYMPATHETIC NERVE. 867 



THE SYMPATHETIC NERVE. 



The Sympathetic Nervous System consists of (1) a series of ganglia, connected 

 together by intervening cords, extending from the base of the skull to the coccyx, 

 one on each side of the middle line of the body, partly in front and partly on each 

 side of the vertebral column ; (2) of three great gangliated plexuses or aggregations 

 of nerves and ganglia, situated in front of the spine in the thoracic, abdominal, and 

 pelvic cavities respectively ; (3) of smaller ganglia, situated in relation with the 

 abdominal viscera ; and (4) of numerous nerve-fibres. These latter are of two 

 kinds: i.-niinnnnli-ntiiH'^ by which the ganglia communicate with each other and 

 with the cerebro-spinal nerves; and distributor^, supplying, in general, all the 

 internal viscera and the coats of the blood-vessels. 



Each gangliated cord may be traced upward from the base of the skull into 

 its cavity by an ascending branch, which passes through the carotid canal, forms 

 a plexus on the internal carotid artery, and communicates with the ganglia on the 

 first and second divisions of the fifth nerve. According to some anatomists, the 

 two cords are joined, at their cephalic extremities, by these ascending branches 

 communicating in a small ganglion (the ganglion of Ribes), situated upon the 

 anterior communicating artery. The ganglia of these cords are distinguished as 

 cervical, dorsal, lumbar, and sacral, and except in the neck they correspond pretty 

 nearly in number to the vertebrae against which they lie. They may be thus 

 arranged : 



Cervical portion . . 3 pairs of ganglia. 

 Dorsal " 12 " 



Lumbar " 4 " " 



Sacral " . .4 or 5 " " 



In the neck they are situated in front of the transverse processes of the verte- 

 brae ; in the dorsal region, in front of the heads of the ribs ; in the lumbar region, 

 on the sides of the bodies of the vertebrse ; and in the sacral region, in front of the 

 sacrum. As the two cords pass into the pelvis they converge and unite together 

 in a single ganglion (ganglion impar) placed in front of the coccyx. Each 

 ganglion may be regarded as a distinct centre, and, in addition to its branches of 

 distribution, possesses also branches of communication which communicate with 

 other ganglia and with the cerebro-spinal nerves. 



The branches of communication between the ganglia are composed of gray 

 and white nerve-fibres, the latter being continuous with those fibres of the spinal 

 nerves which pass to the ganglia. 



The branches of communication between the ganglia and the cerebro-spinal 

 nerves also consist of a white and gray portion, the former proceeding from the 

 spinal nerve to the ganglion, the latter passing from the ganglion to the spinal 

 nerve, so that a double interchange takes place between the two systems. 



The three great gangliated plexuses are situated in front of the spine in the 

 thoracic, abdominal, and pelvic regions, and are named, respectively, the cardiac, 

 the solar or epigastric, and the Tiypogastric plexus. They consist of collections of 

 nerves and ganglia, the nerves being derived from the gangliated cords and from 

 the cerebro-spinal nerves. They distribute branches to the viscera. 



Smaller ganglia are also found lying amidst the nerves, some of them of 

 microscopic size, in certain viscera as, for instance, in the heart, the stomach, and 

 the uterus. They serve as additional centres for the origin of nerve-fibres. 



The branches of distribution derived from the gangliated cords, from the 

 prevertebral plexuses, and also from the smaller ganglia, are principally destined 

 for the blood-vessels and thoracic and abdominal viscera, supplying the involuntary 

 muscular fibre of the coats of the vessels and the hollow viscera, and the secreting 

 cells, as well as the muscular coats of the vessels in the glandular viscera. 



