3. Renal Plexuses.—The right and left renal plexuses are formed by branches which pro ceed from the cceliac and superior mesenteric plexuses, and likewise derive filaments from the aortic plexus. In their course along the renal arteries they receive filaments, which are sent offfrorn the smaller splanchnic nerves, and others from the superior lumbar ganglia. Several small ganglia are present in the nerves of the renal plexus. They divide along with the branches of the renal artery, each arterial branch being generally accompanied by two nervous twigs. From the renal plexus fila ments are sent off, which, with others derived from the cceliac and phrenic plexuses, form the supra-renal plexus destined for the supply of the supra-renal capsule.
4. Spermatic Plexuses.— The right and left spermatic plexuses consist of some delicate nervous filaments, which are derived from the renal plexus. As they pass downwards with the sperrnatic arteries, they receive some ad ditional filaments from the aortic plexus, and appear to give off several filaments to the ureters ; in their course to the testes they are connected with the nerves which accompany the vas defercns. In the female they are dis tributed to the ovaries and uterus.
5. The aortic plexus, situated along the abdo minal aorta, and extending from the superior to the inferior mesenteric arteries, consists of filaments derived from the superior mesenteric and renal plexuses. In its course downwards it also receives branches from the lutnbar gan glia : it terminates in the inferior mesenteric and superior hypogastric plexuses, and also, as has been already stated, contributes to the formation of the spermatic plexus.
6. Inferior Mesenteric Plexus. —The inferior mesenteric plexus, formed by the left lateral portion of the aortic plexus, is less dense and less distinct than the superior plexus of the same name: its fibres present, however, the same whitish aspect and firm consistence, ancl sometimes have small ganglionic enlargements developed upon them. It accompanies the inferior mesenteric artery, dividing along with it, and forming secondary plexuses around its branches, which pass with them to the de scending colon, sigtnoid flexure, and upper half of the rectum. Above, the branches of the inferior mesenteric plexus form communi cations with those derived from the superior mesenteric, and below, with others derived from the superior hypogastric plexus of the left side.
7. Hypogastrie Plexus.—The hypogastric, a single plexus, situated in front of the fifth lumbar vertebra and promontory of the sacrum, between the two common iliac arteries, pre sents an irregularly quadrilateral and flattened a.spect. Nervous branches, about twelve in number, pass down to it on each side from the aortic plexus, and additional filaments are derived from the lumbar ganglia. From the plexus small offsets proceed along the common iliac arteries, and a few join the hemorrhoidal filaments derived from the superior mesenteric plexus : it then divides into a right and left portion, which are continued forwards along the sides of the rectum, to form the inferior hypogastric plexuses.
8. Inferior Hypogastric Plexuses.— These consist of a right and left plexus, formed in the manner just mentioned : they contain several small ganglia. Filaments are likewise sent to them from the sacral ganglia, as well as from two or three of the sacral nerves. These
plexuses are situated upon the sides of the rectum, the plexuses of opposite sides being united by cross branches. From the plexus proceed the following branches. (a) Some hmmorrhoidal branches : these are termed the inferior lImorrhoidal nerves ; they are very delicate and unite with the superior hemor rhoidal branches derived from the inferior mesenteric plexus, and go to supply the rec tum. (b) Vesical plexus . The nerves proceed ing to this plexus come from the lower and anterior portion of the inferior hypogastric plexus, and pass to the sides and lower part of the bladder. The nerves are most nurnerous near the neck of the organ, and have several minute ganglia developed upon them. From the neck numerous branches pass upwards on the sides of the bladder, and are chiefly dis tributed to its muscular coats ; a few, however, may be traced through the muscular to the mucous coat. From the vesical plexus, fila ments are given off which pass to the vesicul seminales, around which they form a plexus; others pass to the vas deferens and ratnify around it, communicating on the spermatic cord with the nerves of the spermatic plexus, while a third portion passes to the prostate gland. The branches which pass to the latter are of considerable size, and form connections with the plexus around the vesicul seminales. Some of the branches sink into the substance of the gland, others are continued forwards to the erectile tissue of the penis, constituting the so-called cavernous nerves, or cavernous plexus. From these branches are distributed to the membranous portion of the urethra. They then continue forwards, passing beneath the arch of the pubis to the root of the penis. By Willer*, they are divided into nervi caver uosi minores, and nervus cavernosus major. The former penetrate the crus of the corpus cavernosus penis, and spread out upon the cells of' the erectile tissue : the latter runs along the dorsum of the penis between the dorsal artery and vein. About the middle of the penis it divides into a number of branches and forms communications with the dorsal branch of the pudic nerve : some of the branches accompany the dorsal vessels and unite with those of the opposite side ; the greater portion, however, penetrate the corpus cavernosum and are distributed to its sub stance.
9. Uterine Plexus.—The nerves destined for the supply of the uterus are derived from the upper and posterior part of the inferior hypo gastric plexus, and also from the superior plexus of the same name. They pass between the folds of the broad ligament in company with the uterine vessels ; before reselling the uterus, however, the greater portion of them separate from the vessels, and are distributed to the substance of the neck and body of the organ. The portion derived from the superior hypogastric plexus appears to be chiefly dis tributed to the fundus of the organ : a fila ment also passes, according to Dr. Beck*, from the ovarian artery to the fundns of the uterus. Besides the branches above mentioned there are others, according to Dr. Beck, derived also from the hypogastric plexus, which assume a plexiform arrange ment around the vessels, and are characterised by the presence of several minute ganglia.