on each side of the spinal column and tied together below; for both chains of ganglia end in the same ganglion in the pelvis. Some of the fibers from the spinal cord pass through these ganglia on their way to the viscera, losing their white sheaths in the ganglia and emerging as gray fibers. The spinal cord and brain with the fibers which do not pass through the double chain of ganglia are called the cerebro-spinal system. The double chain of ganglia and the fibers which go through them are called the ganglionic or sympathetic system.
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Fig. 116.—Diagram of Sympathetic System showing double chain of ganglia; also plexus at heart and solar plexus.
Why these Nerves are called the Sympathetic System.—These nerves, after leaving the double chain of ganglia, form many intricate networks of ganglia and fibers. Each network is called a plexus (Fig. 116). The largest of the plexuses is just back of the stomach, and is called the solar plexus. A blow upon the stomach may paralyze this plexus and cause sudden death. The plexuses and fibers connect the viscera so perfectly that one organ cannot suffer without the others changing their activity, or sympathizing with it. An overloaded stomach causes the heart to beat faster and send it more blood; a loss of appetite usually accompanies illness and allows the stomach to rest. This sympathy is necessary, for if one organ is
