HYPOGASTRIC AND PELVIC PLEXUSES. 377 



colon, and assists in supplying the rectum. The nerves of this plexus, like those of 

 the superior mesenteric plexus, are firm in texture and of a whitish colour. 



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. 



On the branches of the coeliac and mesenteric plexuses Pacinian corpuscles are often 

 present. They are very variable in number, and are not so numerous or regular in man as in 

 the cat. Their most frequent seat is in the loose tissue behind the pancreas. 



HYPOQASTRIC 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 the prolongations 

 of the aortic plexus on each side, which receive considerable branches from the 

 lumbar ganglia, and, after crossing the common iliac artery, interlace in the form of 

 a flat plexiform mass placed in front of the lowest lumbar vertebra. The plexus 

 contains no distinct ganglia. At the lower end it divides into two parts, which 

 are directed downwards, one to each side of the pelvic viscera, and form the pelvic 

 plexuses. 



PELVIC PLEXUS. 



The pelvic or inferior hypogasfcric plexuses (fig. 234, pl\ 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, continued 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, sometimes also the second. Small ganglia are formed at the places of union 

 of the spinal nerves, as well as elsewhere in the plexus. 



From the plexus so constituted, numerous nerves are distributed to the pelvic 

 viscera. They correspond in great measure with the branches of the internal iliac 

 artery, and vary with the sex ; thus, besides haemorrhoidal 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 Fallopian tube. 



The nerves distributed to the urinary bladder and the vagina contain a larger 

 proportion of spinal fibres than those furnished to the other pelvic viscera. 



Haemorrhoidal plexus. These slender nerves proceed from the upper part of 

 the pelvic plexus. They join with the nerves (superior haemorrhoidal) which descend 

 with the inferior mesenteric artery, and penetrate the coats of the rectum. 



Vesical plexus. The nerves of the urinary bladder are very numerous. They 

 are directed from the lower part of the pelvic plexus to the side and lower part of 

 the bladder. At first these nerves accompany the vesical blood-vessels, but after- 

 wards they leave the vessels, and subdivide into minute branches before perforating 

 the muscular coat of the organ. The lower part of the ureter is also supplied by 

 these nerves ; and secondary plexuses are given in the male to the vas deferens and 

 the vesicula seminalis. 



The nerves of the vas deferens ramify round that tube, and communicate in the 

 spermatic cord with the nerves of the spermatic plexus. Those furnished to the 

 vesicuta seminalis form an interlacement on the vesicula, and some branches 



