10 64 THE NERVE SYSTEM 



nerves, or from the third and fourth or even fourth and fifth sacral nerves, and is 

 of small size. When present, it pierces the lower part of the great sacrosciatic 

 ligament, and, winding around the lower border of the Gluteus maximus, supplies 

 the integument covering the inner and lower part of that muscle. When absent, 

 its place is taken either by a cutaneous branch of the small sciatic, or by the greater 

 coccygeal perforating nerve of Eisler. 



The Pudic Nerve (n. pudendus) (Figs. 774 and 776) derives its fibres from the 

 anterior branches of the second, third, and fourth sacral nerves. It leaves the 

 pelvis below the Pyriformis through the great sacrosciatic foramen. It then crosses 

 the spine of the ischium, and enters the pelvis through the lesser sacrosciatic 

 foramen. It accompanies the pudic vesses upward and forward along the outer 

 wall of the ischiorectal fossa, being contained in a sheath of the obturator fascia, 

 termed Alcock's canal, and divides into two terminal branches, the perineal nerve, 

 and the dorsal nerve of the penis or clitoris. Before its division it gives off the 

 inferior hemorrhoidal nerve. 



The inferior hemorrhoidal nerve (n. hemorrhoidalis inferior^) is occasionally 

 derived separately from the sacral plexus (3d S.). It passes across the ischio- 

 rectal fossa, with its accompanying vessels, toward the lower end of the rectum, 

 and is distributed to the Sphincter ani externus and to the integument around the 

 anus. Branches of this nerve communicate with the inferior pudendal and super- 

 ficial perineal nerves at the fore part of the perineum. 



The perineal nerve (n. perinei), the inferior and larger of the two terminal 

 branches of the pudic, is situated below the pudic artery. It accompanies the 

 superficial perineal artery in the perineum, dividing into cutaneous and muscular 

 branches. 



The cutaneous branches (superficial perineal) are two in number, posterior and 

 anterior. The posterior or external branch pierces the base of the triangular liga- 

 ment of the urethra, and passes forward along the outer side of the urethral 

 triangle in company with the superficial perineal artery; it is distributed to the 

 skin of the scrotum (nn. scrotales posteriores). It communicates with the inferior 

 hemorrhoidal, the inferior pudendal, and the other superficial perineal nerve. 

 The anterior or internal branch also pierces the base of the triangular ligament, and 

 passes forward nearer to the middle line, to be distributed to the inner and back 

 part of the scrotum. Both these nerves supply the labium majus in the female. 



The muscular branches are distributed to the Transversus perinaei, Accelerator 

 urinae, Erector penis, and Compressor urethrae. A distinct branch is given off 

 from the nerve to the Accelerator urinae, pierces this muscle, and supplies the 

 corpus spongiosum, ending in the mucous membrane of the urethra. This is the 

 nerve to the bulb. 



The Dorsal Nerve of the Penis (n. dorsalis penis) is the deepest division of the 

 pudic nerve; it accompanies the pudic artery along the ramus of the ischium; it 

 then runs forward along the inner margin of the ramus of the os pubis, between 

 the superficial and deep layers of the triangular ligament. Piercing the superficial 

 layer, it gives a branch to the corpus cavernosum, and passes forward, in company 

 with the dorsal artery of the penis, between the layers of the suspensory ligament, 

 on to the dorsum of the penis, along which it is carried as far as the glans on which 

 it ends. 



In the female the dorsal nerve is very small, and supplies the clitoris (//. dorsalis 

 clitoridis). 



The visceral branches arise from the third and fourth, and sometimes the second, 

 sacral nerves and are distributed to the bladder and rectum, and, in the female, 

 to the vagina; they communicate with the pelvic plexuses of the sympathetic. 



The muscular branches are derived from the fourth sacral, and supply the Ivevator 

 ani, Coccygeus, and Sphincter ani externus. The branches to the Levator ani 



