THE NERVOUS SYSTEM 2$I 



middle, and inferior cervical; twelve in the dorsal region; 

 four in the lumbar region, and four in the sacral region. 



Bach ganglion is considered as a distinct center, receiv- 

 ing and giving branches in four different directions viz., 

 superior, or ascending, to communicate with the ganglion 

 above; inferior, or descending, to communicate with the 

 ganglion below; external, to communicate with the spinal 

 nerves ; and internal, to communicate with the sympathetic 

 filaments of the opposite side and become distributed to 

 the viscera. 



Fig. 114 illustrates the several portions of the sympa- 

 thetic nerve. As has been said, this nerve is one of or- 

 ganic life, for there is no organ in the whole body but 

 becomes affected when the function of this nerve is dis- 

 turbed; from this it may be seen how sympathy exists 

 between the several structures ; this has already been dealt 

 with in another part of this chapter. 



seen descending from the vagus and recurrent nerves; co, right, or posterior, 

 and co', left, or anterior, coronary plexus; o, esophageal plexus in long 

 meshes on the gullet ; sp, great splanchnic nerve formed by branches from the 

 fifth, sixth, seventh, eighth, and ninth dorsal ganglia; +, small splanchnic 

 from the ninth and tenth ; + +, smallest, or third, splanchnic from the elev- 

 enth ; the first and second of these are shown joining the solar plexus, so ; the 

 third descending to the renal plexus, re ; connecting branches between the 

 solar plexus and the vagi are also represented pn', above the place where 

 the right vagus passes to the lower or posterior surface of the stomach ; pn" ', 

 the left distributed on the anterior or upper surface of the cardiac portion 

 of the organ : from the solar plexus large branches are seen surrounding 

 the arteries of the celiac axis, and descending to ms, the superior mesenteric 

 plexus; opposite this is an indication of the suprarenal plexus; below re 

 (the renal plexus) the spermatic plexus is also indicated; ao, on the front of 

 the aorta, marks the aortic plexus, formed by nerves descending from the 

 solar and superior mesenteric plexuses and from the lumbar ganglia ; mi, the 

 inferior mesenteric plexus surrounding the corresponding artery ; hy, hypo- 

 gastric plexus placed between the common iliac vessels, connected above with 

 the aortic plexus, receiving nerves from the lower lumbar ganglia, and dividing 

 below into the right and left pelvic or inferior hypogastric plexuses ; pi, the 

 right pelvic plexus ; from this the nerves descending are joined by those from 

 the plexus on the superior hemorrhoidal vessels, mi' , by nerves from the 

 sacral ganglia, and by visceral nerves from the third and fourth sacral spinal 

 nerves, and there are thus formed the rectal, vesical, and other plexuses, 

 which ramify upon the viscera, as toward ir, and v, the rectum and bladder. 



