PELVIC PLEXUS. 671 



plexus. It surrounds the inferior mesenteric artery, and divides into a number 

 of secondary plexuses, which are distributed to all the parts supplied by the 

 artery, viz., the left colic and sigmoid plexuses, which supply the descending 

 and sigmoid flexure of the colon; and the superior hasrnorrhoidal plexus, 

 which supplies the upper part of the rectum, and joins in the pelvis with 

 branches from the left hypogastric plexus. 



THE LUMBAR PORTION OF THE SYMPATHETIC. 



The Lumbar Portion of the Sympathetic is siiuated in front of the vertebral 

 column, along the inner margin of the Psoas muscle. It consists usually of 

 four ganglia, connected together by interganglionic cords. The ganglia are of 

 small size, of a grayish color, shaped like a barley-corn, and placed much nearer 

 the median line than the thoracic ganglia. 



The superior and inferior branches of the lumbar ganglia serve as communi- 

 cating branches between the chain of ganglia in this region. They are usually 

 single, and of a white color. 



The external branches communicate with the lumbar spinal nerves. From the 

 situation of the lumbar ganglia, these branches are longer than in the other 

 regions. They are usually two in number for each ganglion, and accompany 

 the lumbar arteries around the sides of the bodies of the vertebra, passing 

 beneath the fibrous arches from which some of the fibres of the Psoas muscle 

 arise. 



The internal branches pass inwards, in front of the aorta, and form the lumbar 

 aortic plexus, already described. Other branches descend in front of the com- 

 mon iliac arteries, and join, over the promontory of the sacrum, to form the 

 hypogastric plexus. Numerous delicate filaments are also distributed to the 

 bodies of the vertebrae, and the ligaments connecting them. 



PELVIC PORTION OP THE SYMPATHETIC. 



The Pelvic Portion of the Sympathetic is situated in front of the sacrum, 

 along the inner side of the anterior sacral foramina. It consists of four or five 

 small ganglia on each side, connected together by interganglionic cords. 

 Below, these cords converge and unite on the front of the coccyx, by means of 

 a small ganglion (ganglion impar). 



The superior and inferior branches are the cords of communication between 

 the ganglia above and below. 



The external branches, exceedingly short, communicate with the sacral nerves. 

 They are two in number to each ganglion. The coccygeal nerve communicates 

 either with the last sacral, or coccygeal ganglion. 



The internal branches communicate, on the front of the sacrum, with the 

 corresponding branches from the opposite side; some, from the first two gan- 

 glia, pass to join the pelvic plexus, and others form a plexus, which accompa- 

 nies the middle sacral artery. 



The hypogastric plexus supplies the viscera of the pelvic cavity. It is situ- 

 ated in front of the promontory of the sacrum, between the two common iliac 

 arteries, and is formed by the union of numerous filaments, which descend on 

 each side from the aortic plexus, from the lumbar ganglia, and from the first 

 two sacral ganglia. This plexus contains no ganglia, and bifurcates, below, into 

 two lateral portions, which form the inferior hypogastric, or pelvic plexuses. 



INFERIOR HYPOGASTRIC, OR PELVIC PLEXUS. 



The Inferior Hypogastric, or Pelvic Plexus, is situated at the side of the 

 rectum and bladder in the male, and at the side of the rectum, vagina, and 

 bladder, in the female. It is formed by a continuation of the hypogastric 

 plexus, by bran'ches from the second, third, and fourth sacral nerves, and by a 



