THE NERVOUS SYSTEM OF MAN. 69 



terns, the axial and the ganglionic, are brought into re- 

 lation with one another (Fig. 38, en en). (4) From the 

 sympathetic ganglia on each side there go nerves to the 

 visceral region, where are performed the most impor- 

 tant functions. There the nerves from each side unite 

 to form plexuses or networks — i. e., the nerves cross one 

 another in every direction, uniting at the crossings and 

 forming ganglia there, and from these again come 

 smaller branches going to all the important viscera and 

 controlling their functions (Fig. 38,//). 



The Plexuses. — Beginning above and going down- 

 ward, the principal plexuses are (1) the carotid and (2) 

 the pharyngeal, small plexuses with their ganglia con- 

 trolling the throat viscera (Fig. 38,^/1 and 2); (3) the 

 cardiac (plexus in the thorax) with its ganglia, control- 

 ling the action of the heart (Fig. 38,^/3); (4) in the 

 stomach region the epigastric or solar plexus with its 

 ganglia, controlling the action of the stomach, spleen, 

 and liver (Fig. 38,^/4) ; (5) the hypogastric plexus and 

 its ganglia, controlling the functions of the pelvic vis- 

 cera (Fig. 38, // 5). Into the cardiac and epigastric 

 plexus enter the branches of the pneumogastric nerve 

 from the medulla, and play an important part in the 

 control of the heart, lungs, and stomach. 



Function. — The function of this system is obscure, 

 but certainly largely connected with the processes of nu- 

 trition, secretion, etc., or organic functions. Its func- 

 tion is doubtless also reflex, so far as the organs to 

 which its nerves are distributed are concerned, but 

 whether by its own fibers or by means of fibers derived 

 from the axial system is more doubtful. It seems to 

 control nutrition and secretion by controlling the blood 

 supply ; and this is done by means of certain fibers — 

 vasomotor fibers — distributed to the capillary blood ves- 

 sels — vasomotor nerves. Cutting the vasomotor nerves 



