THE CCELTAC, AORTIC, AND MESENTEPJC PLEXUSES. 6il 



connected with the semilunar ganglia and renal plexuses, whicli are extended on 

 the sides of the aorta, and which meet in several larger communicating branches 

 over the middle of that vessel. It is joined by branches from some of the lumbar 

 ganglia, and presents not unfrequently one or more distinct ganglionic enlarge- 

 ments towards its centre. 



The aortic plexus furnishes the inferior mesenteric jjlexus and pai-t of the 

 Dpermatic, gives some filaments to the lower vena cava, and ends below in the 

 hypogastric plexus. 



Inferior Mesenteric Plexus. — This plexus is derived principally from the left 

 lateral part of the aortic plexus, and closely surrounds with a network the 

 inferior mesenteric artery. It distributes nerves to the left or descending part 

 and the sigmoid flexure of the colon, and assists in supplying the rectum. The 

 nerves of this plexus, like those of the superior mesenteric plexus, are firm in 

 textui-e and of a whitish colom-. 



The highest branches (those on the left colic artery) are connected with the 

 last branches (middle colic) of the superior mesenteric plexus, while others in. 

 the pelvis unite with offsets derived from the pelvic plexus. 



HYPOGASTRIC PLEXUS. 



The hypogastric plexus, the assemblage of nerves destined for the 

 supply of the viscera of the pelvis, lies invested in a sheath of dense 

 connective tissue, in the interval between the two common iliac arteries. 

 It is formed by eight or ten nerves on each side, which descend from the 

 aortic plexus, receiving considerable branches from the lumbar ganglia, 

 and, after crossing the common iliac artery, interlace in the form of a flat 

 plexiform mass placed in fi-ont of the lowest lumbar vertebra. The 

 plexus contains no distinct ganglia. At the lower end it divides into 

 two parts, which are directed forwards, one to each side of the pelvic 

 viscera, and form the pelvic plexuses. 



PELVIC PLEXUS. 



The pelvic or inferior hypogastric plexuses, one on each side, are 

 placed in the lower part of the pelvic cavity by the side of the rectum, 

 and of the vagina in the female. The nerves, prolonged from the 

 hypogastric plexus, enter into repeated communications as they descend, 

 and form at the points of connection small knots, which contain a 

 little ganglionic matter. After descending some way, they become 

 united with branches of the spinal nerves, as well as with a few offsets 

 of the sacral ganglia, and the union of all constitutes the pelvic plexus. 

 The spinal branches, which enter into the plexus, are furnished from 

 the third and fourth sacral nerves, especially the third ; and filaments 

 are likewise added from the first and second sacral nerves. Small 

 ganglia are formed at the places of union of the spinal nerves, as well 

 as elsewhere in the plexus (plexus gangliosus — Tiedemann). 



From the plexus so constituted, numerous nerves are distributed to 

 the pelvic viscera. They correspond with the branches of the internal 

 iliac artery, and vary with the sex ; thus, besides hfemorrhoidal and 

 vesical nerves, which are common to both sexes, there are nerves special 

 to each : — namely, in the male for the prostate, vesicula seminalis, and 

 Vas deferens ; in the female, for the vagina, uterus, ovary, and Fallo- 

 pian tube. 



The nerves distributed to the urinary bladder and the vagina contain 

 a larger proportion of spinal nerves than those furnished to the other 

 pelvic viscera. 



VOL. I. T T 



