ABDOMEN. 273 



will come from plexuses on the artery ; these plexuses will originate in ganglia 

 near the origin of the artery ; they will take the name of the artery and trace 

 their own origin to the hypogastric plexus. We shall find, in the thorax, the 

 heart and lung concerned in the circulation of the blood and its purification 

 respectively. These organs receive their nourishment through arteries, and 

 their arteries are attended by nerves, which nerves have their origin in plexuses ; 

 these plexuses spring from ganglia near the origin of the artery, and these 

 ganglia trace their own origin to the cardiac plexus. 



There is, then, one great sympathetic depot for the organs in the thorax, called 

 cardiac pie. rus ; one in the abdomen, called solar plexus ; one in the pelvis, called 

 hypogastric plexus. This arrangement is simply to make possible a physiological 

 division of labor. Remember, then : the manner of distribution of sympathetic 

 nerves is always the same in every region of the body ; branches, plexuses, and 

 ganglia take the name of the artery ; there are three large plexuses (i) cardiac, 

 (2) solar, (3) hypogastric ; there are as many small plexuses as there are 

 arteries to supply viscera and these small plexuses all draw their influence 

 from the three large plexuses. 



In view of what we have found, and what we shall find, let us gain a general 

 idea of the sympathetic system in the following questions and answers : 



1. Is the sympathetic a system, separate and entire, and independent of the 

 ccrebro-spinal ? 



No ; sympathetic nerves are only nerves, branches of the spinals, set aside 

 to supply organs. 



2. Of ivhat docs ttic sympathetic system consist f 



(i) Of gangliated cord, in the form of a horse-collar, communicating on the 

 anterior communicating artery above and on the coccyx below ; (2) of spinal 

 branches, called rami communicantes two from each spinal nerve ; (3) of three 

 prevertebral plexuses cardiac, solar, and hypogastric ; (4) of branches of distri- 

 bution ; (5) of plexuses and ganglia that take the name of the arteries on which 

 found. 



3 . Can iv e see the nerves and ganglia / 



Yes ; in the thorax behind the pleura, and located opposite the heads of the 

 ribs, you can seethe ganglia ; you can also find the two communicating branches 

 from the spinal nerves ; also the cord extending from one nerve to another. 



The Hypogastric Plexus. In the lumbar region you will find the gangli- 

 ated cord on the front of the bodies of the vertebrae, along the inner margin of 

 the psoas magnus. You can trace branches to the lumbar nerves behind the 

 psoas magnus. You will see numerous branches from the lumbar cords, uniting 

 with branches coming down from above to form the hypogastric plexus. This 

 is between the common iliac arteries and passes down to form the pelvic plexus. 



