766 



THE NEKVOUS SYSTEM. 



PLEXUS PELVINI. 



The hypogastric nerves form the continuation of the aortic plexus into the 

 pelvic cavity. They consist of numerous plexiform bundles of nerve-fibres which 

 descend along the front and back of the bifurcation of the aorta and the origin of 

 the common iliac arteries, and over the sacral promontory, where, becoming in- 

 extricably mingled, they constitute the hypogastric plexus. 



The hypogastric plexus is continued downwards in front of the sacrum on each 

 side of the rectum, and ends in the pelvic plexuses. 



The pelvic plexuses are formed by the separation of the hypogastric plexus 

 into two halves at the sides of the rectum. Each is joined by fibres from the 

 upper portion of the pelvic part of the sympathetic trunk, and by the visceral 

 branches (white rami communicantes) from the second and third or third and 

 fourth sacral nerves. Accompanying the hypogastric artery and its branches, 

 each pelvic plexus gives off subordinate plexuses for the pelvic viscera. 



a. Plexus Hsemorrhoidalis The haemorrhoidal plexus supplies the rectum, and 

 joins the superior hsemorrhoidal plexus from the inferior mesenteric plexus. 



&. Plexus Vesicalis. The vesical plexus accompanies the vesical arteries to the 

 bladder-wall. Besides supplying the muscular wall and mucous membrane of the 

 bladder, it forms subordinate plexuses for the lower part of the ureter, the vesicula 

 seminalis, and the ductus deferens. 



c. Plexus Prostaticus. The prostatic plexus is of considerable size. It is placed 

 on both sides of the gland, and, in addition to supplying its substance and the 

 prostatic urethra, it sends offsets to the neck of the bladder and the vesicula 

 seminalis. It is continued forwards on each side to form the plexus cavernosus penis 

 (cavernous plexus of the penis). Bundles of nerves pierce the layers of the fascia 

 of the urogenital diaphragm, and, after supplying the membranous urethra, 

 give off branches which enter and supply the corpus cavernosum penis. The 

 cavernous nerves communicate with branches of the pudendal nerve and give 

 offsets to the corpus cavernosum urethrae and the penile portion of the urethra. 



d. Plexus Uterovaginalis. The uterine plexus passes upwards with the uterine 



artery between the layers of the 

 broad ligament, and is dis- 

 tributed to the surfaces and 

 substance of the organ. It com- 

 municates between the layers of 

 the broad ligament with the 

 plexus of the ovarian artery. 



The vaginal plexus is formed 

 mainly by the visceral branches 

 of the sacral nerves entering 

 the pelvic plexus. It supplies 

 the wall and mucous membrane 

 of the vagina and urethra, and 

 provides a cavernous plexus for 

 the clitoris. The uterine and 

 vaginal plexuses of the female 

 correspond to the prostatic plexus 

 of the male. 



THE MORPHOLOGY OF THE 

 SYMPATHETIC SYSTEM 



S P I. I 





Sy. 



From a consideration of its struc- 



Fio. 642. SECTION THROUGH THE SYMPATHETIC TRUNK 



OF AN EMBRYO. 



Showing the connexion with the ganglion (Sy) of the white ture > functions, and development, there 

 ramus communicans (Spl) ; (a) a portion of the ramus joining appear to be two separate structures 

 the ganglion ; (|8) fibres passing over the trunk, accompanied represented in the sympathetic nerve 

 by a stream of cells ; (7) continuous with those of the gan- system the spinal and the sym- 

 glion ; (Ao) Aorta. pathetic elements. The structure of 



the system presents a union of two 



distinct elements fibres of cerebro - spinal origin and "sympathetic" cells and fibres. While 

 the function of the sympathetic trunk and its branches seems to be dependent upon the 



