766 



SPINAL NERVES. 



the plexus gives off a series of anterior and 

 posterior branches. Of the former are ob- 

 served, a nerve for the obturator internus, 

 and the internal piulic : of the latter, the su- 

 perior glutaeal, inferior glutaeal, nerves for the 

 pyriformis, gemelli, and quadratus femoris. 



* The nerve for the obturator internus takes its 

 origin from the upper and outer part of the 

 plexus, being derived from the lurnbo-sacral 

 and first sacral. It passes behind the spine 

 of the iscbium, 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 >l 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 (Perinaeal nerve su- 

 perficial perinaeal) perforates the obturator 

 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 perinceal, 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 urinae 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 perinaeal, 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 perinaei muscle. Some are 

 sent inwards to the external sphincter, le- 

 vator ani, and accelerator urinae: others to 

 the erector penis ; the termination of the nerve 

 being represented by a small branch, whicli 

 passes into the substance of the bulbous por- 

 tion of the urethra. 



The pudic nerve not unfrequently gives off 

 the inferior htemorrhoidal (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 perinaeal, 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 haemorrhoidal, when not a 

 branch of the pudic, is given off from the 

 sacral plexus. 



The superior ghdteal 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. 



The superior branch takes the course of 

 the superficial trunk of the corresponding 

 artery, courses along the convex border of 

 the glutaeus minimus, and supplies principally 

 the upper and back part of the glutaeus me- 

 dius. The inferior branch is directed down- 

 wards, forwards, and outwards between the 

 two glutaei, and, after a short course, divides 

 into a superficial branch, supplying the upper 

 and anterior part of the glutaeus medius ; and 

 a deep branch running across the glutaeus 

 minimus, supplying it and the medius, and 

 terminating near the great trochanter, by 

 entering the substance of the tensor vaginae 

 femoris, at the lower, inner, and back part of 

 its sheath. 



The inferior glutceal nerve (lesser sciatic) 

 arises from the back part of the sacral plexus 

 by one or more roots. It emerges from the 

 pelvis at the lower and anterior part of the 

 great sacro-sciatic notch, either as a single, 

 or as two, or three, trunks, below the pyri- 

 formis, and about a quarter of an inch behind 

 and internal to the great sciatic. It is directed 

 between the tuberosity of the ischium, and 

 the great trochanter, but nearer the former, 



