300 PHYSIOLOGY CHAP. 



Anatomically the following parts can be distinguished : 



A. Two nerve cords, running along the ventral surface of the 

 vertebral column, from the atlas to the coccyx, which are segmentally 

 interrupted at given points in their course by nodes or ganglia, 

 and are known as the gangliated cords of the sympathetic 

 (Fig. 167, p. 279). Each is subdivided into cervical, thoracic, 

 lumbar, and sacral portions. 



The cervical part has three ganglia : superior, middle, and 

 inferior. The thoracic part contains eleven or twelve ganglia, the 

 first two or three of which are usually united into a single ganglion 

 the stellate ganglion while the lumbar and sacral parts have 

 five or sometimes only four ganglia each. The ends of the two 

 chains converge and unite behind the coccyx in a small single 

 node, the so-called unpaired coccygeal ganglion of Walter. 



Each of these ganglia, which Gaskell termed vertebral or lateral 

 from their position, gives off three branches : (a) fibres which 

 connect the ganglion with the neighbouring spinal nerves (rami 

 communicantes). Of these, there are two classes : the white rami, 

 which consist principally of myelinated nerve-fibres ; and the grey 

 rami, composed mainly of non-medullated fibres. These are the 

 only paths by which the sympathetic system is united to the 

 cerebrospinal axis. (&) Branches which connect the several 

 ganglia among themselves, and consist partly of medullated, 

 partly of non-medullated, fibres, (c) Branches that either run 

 directly to the peripheral organs or to ganglia of the sympathetic 

 system, which lie more peripherally. 



B. The large plexuses of the sympathetic, which innervate the 

 viscera and lie distal to the ganglion chain near the large blood- 

 vessels. They consist of a network of nerve-fibres, which arise for 

 the most part in the gangliated cord, but partly also from the 

 vagus and from ganglia within the plexus. The most important 

 are : the cardiac plexus ; the caeliac plexus, also called from its 

 radiate appearance the solar plexus, which is the largest and 

 richest in the body, and is formed principally of the splanchnic 

 nerves from branches given off by the 5th or 6th to the 9th or 

 10th thoracic ganglia; and the hypogastric plexus. 



Gaskell gave the name of pre-vertebral or collateral to the 

 ganglia of the large plexuses to distinguish them from those of 

 the ganglion chain, which he termed vertebral or lateral. Besides 

 these ganglia smaller groups of cells lie more peripherally along 

 the course of the different nerve trunks, before these enter the 

 visceral organs they innervate ; Gaskell termed these ganglia of 

 the third order terminal ganglia. 



C. Besides the sympathetic system proper, there are other 

 central and peripheral nervous structures with similar functional 

 properties, which must be discussed along with it. Langley 

 includes in the sympathetic system all the nerves and ganglia 



