The nerve for the obturator intern= takes its origin from the upper and outer part of the plexus, being derived from the lumbo-sacral and first sacral. It passes behind the spine of the ischiutn, and the lesser sacro-sciatic liga ment, reenters the pelvis at the lesser sciatic notch, and is distributed by three or four branches within the inner aspect of the muscle.
The internal pudic nerve, arising from the lower part of the plexus, and generally de rived from the third and fourth nerves, passes behind the spine of the ischium, internal to the pudic artery, in company with the preceding, and then enters the ischio-rectal fossa, where it divides into a superior and inferior branch.
The superior branch (the dors nerve of the penis) ascends in company with the internal pudic artery, but above it, between the obtu rator internus and the levator ani, to pass between the two layers of the triangular liga ment : perforating the anterior layer imme diately under the pubic arch it gains the dor sum of the penis, in which situation it is placed in the fold of the suspensary ligament, and in clines inwards to the median line. Having given off one or more external branches, which run superficially as long and slender fila ments along the upper and outer part of the penis, supply the corpora cavernosa -and their integument, and are conducted as far as the prepuce, the nerve continues its forward direc tion. It passes to the side of the median line, sends numerous filaments to the skin ; commu nicating branches to the nerve of the opposite side; and some to accompany the dorsal vein of the penis; and at the root of the glans penis, penetrates deeply between it and the corpus cavernosum,and terminates by sending numer ous filaments throughout its substance.
The inferior branch (Perinmal nerve — su perficial perinmal) perforates the obtnrator fascia at the inner and anterior part of the tuberosity of the ischium, and divides into two branches, an anterior and superior, having previously given off' a posterior branch, named by Cruveilhier the external perinwal, which passes through the obturator fascia behind the tuberosity of the ischium. It runs in company with, but external to, the anterior branch, superficial to the crus of the penis, and terminates by supplying the lower and anterior part of the scrotum where it gives off filaments on the inside to unite with some from the anterior branch, on the outside to communicate with the long inferior puden dal branch of the lesser sciatic. The an
terior branch passes in the interval between the accelerator urinm and the erector penis, internal to the preceding, and inclines a little forwards and inwards, and ends in a series of long filaments, which communicate laterally with the external perinmal, and send branches to the middle of the lower and anterior part of the skin of the scrotum, some of them being conducted along the skin at the lower aspect of the penis as far as the prepuce. The su perior branch soon divides into a series of muscular branches, after having passed above the transversalis perinmi muscle. Sonie are sent inwards to the external sphincter, le vator ani, and accelerator urinw : others to the erector penis ; the termination of the nerve being represented by a small branch, which passes into the substance of the bulbous por tion of the urethra.
The pudic nerve not unfrequently gives off the inferior hceniorrhoidat (anal), which passes along its inner side, is directed through the obturator fascia to the ischio-rectal space which it traverses to the side of the rectum, and at the upper border of the external sphincter divides into a series of filaments, the anterior of which communicate with the superior branch of the perinal, and supply the front of the sphincter and the skin over it. The middle and posterior series supply the sides and back part of the sphincter. Some filaments are given off externally, which pass over the great trochanter, and communicate with the long inferior pudendal nerve. The skin about the anus is also freely supplied.
The inferior hxmorrhoidal, when not a branch of the pudic, is given off' from the sacral plexus.
The superior enteral nerve is derived either from the lumbo-sacral nerve only, or from two distinct roots, the one from it and the other from the back part of the first sacral nerve. The former source of' origin usually obtains ; and in the latter the root from the sacral nerve is not more than half as long as that from the lumbo-sacral. It passes out as a single trunk at the upper and fore part of the border of the sacro-sciatic notch, in front, and above the pyriformis, and divides into a superior and inferior branch.