THE SACRAL PLEXU8. 861 



enters the muscle at the upper part of its posterior surface ; the small branch to the 

 Gemellus inferior and Quadratus femoris arises from the lumbo-sacral cord and 

 first sacral nerve : it passes through the great sacro-sciatic foramen, and courses 

 down beneath the Gemelli and tendon of the Obturator internus, and sup- 

 plies the muscles on their deep or anterior surface. It gives off an articular 

 branch to the hip-joint. Another articular branch is occasionally derived from 

 the upper part of the great sciatic nerve. 



The Superior Gluteal Nerve (Fig. 510) arises from the back part of the lumbo- 

 sacral cord and first sacral nerve : it passes from the pelvis through the great 

 sacro-sciatic foramen above the Pyriformis muscle, accompanied by the gluteal 

 vessels, and divides into a superior and an inferior branch. 



The superior branch follows the line of origin of the Gluteus minimus, and 

 supplied the Gluteus medius. 



The inferior branch crosses obliquely between the Gluteus minimus and 

 medius, distributing filaments to both these muscles, and terminates in the Tensor 

 vaginae femoris, extending nearly to its lower end. 



The Inferior Gluteal arises from the lumbo-sacral cord and first and second 

 sacral nerves, and is often intimately connected with the small sciatic at its origin. 

 It passes out of the pelvis through the great sciatic notch, beneath the Pyriformis 

 muscle, and, dividing into a number of branches, enters the Gluteus maximus 

 muscle on its under surface. 



The Perforating Cutaneous Nerve is derived from the second and third sacral 

 nerves. It pierces the great sacro-sciatic ligament and winds round the lower 

 border of the Gluteus maximus muscle to supply the skin of the buttock. 



The Pudic Nerve arises from the lower cord of the sacral plexus (sometimes 

 containing fibres derived from the second and even first sacral nerves), and leaves 

 the pelvis, through the great sacro-sciatic foramen, below the Pyriformis. It then 

 crosses the spine of the ischium, and re-enters the pelvis through the lesser sacro- 

 sciatic foramen. It accompanies the pudic vessels upward and forward for a short 

 distance along the outer wall of the ischio-rectal fossa, and then divides into 

 three branches, the perineal nerve, the dorsal nerve of the penis, and the inferior 

 haemorrhoidal nerve. 



The inferior hcemorrhoidal nerve is occasionally derived separately from the 

 sacral plexus. It passes across the ischio-rectal fossa, with its accompanying ves- 

 sels, toward the lower end of the rectum, and is distributed to the integument 

 round the anus. Branches of this nerve communicate with the inferior pudendal 

 and superficial perineal nerves at the fore part of the perinaeum. 



The perineal nerve, the largest of the branches of the pudic, is situated 

 below the pudic artery. It accompanies the superficial perineal artery in the 

 peringeurn, dividing into cutaneous and muscular branches. 



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

 and anterior. The posterior or external branch passes forward along the outer 

 side of the perineal space parallel to the inferior pudendal nerve, and is distrib- 

 uted to the skin of the scrotum. It communicates with the inferior hgemorrhoid- 

 al, the inferior pudendal, and the other superficial perineal nerve. The anterior 

 or internal branch passes forward nearer to the middle line, to be distributed to 

 the inner and back part of the scrotum. Both these nerves supply the labia 

 majora in the female. 



The muscular branches are distributed to the Transversus perinaei, Accelerator 

 urinre. Erector penis, External sphincter and Levator ani, and Compressor urethrae. 

 A distinct branch is given off from the nerve to the Accelerator urinae, which 

 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 is the deepest division of the pudic nerve ; it 

 accompanies the pudic artery along the ramus of the ischium : piercing the pos- 

 terior layer of the deep perineal fascia, it runs forward along the inner margin 

 of the ramus of the os pubis, between the two layers of the deep fascia. It then 



