THE PUDENDAL PLEXUS. 



1347 



Cutaneous brs. from 

 post, sacral nerves 



Itif. pudendal 

 nerve, and a glu- 

 teal cutaneous br. 

 of small sciatic 



Small sciatic nerve — 



posterior portion of the external sphincter and distributes sensory 



integument over the 



base of the ischio- Fig. 1124. 



rectal fossa and the tip 



of the coccyx. 



Variation. — This 

 nerve, instead of pierc- 

 ing the coccygeus, may 

 pass between that nms 

 cle and the levator ani. 



The nerve to the 

 levator ani is derived 

 usually from the third 

 and fourth, sometimes 

 the second and third, 

 sacral nerves and en- 

 ters the muscle by 

 piercing its mesial 

 surface. 



3. The perfo- 

 rating cutaneous 

 nerve (Fig. 1126) is 

 an inconstant branch, 

 being found in about 

 two thirds of the 

 bodies examined. It 

 springs from the dor- 

 sal aspect of the 

 second and third sac- 

 ral nerves and at its 

 point of origin may 

 be associated with the 

 pudig or the small 

 sciatic. Passing 

 downward and back- 

 ward it pierces the 

 great sacro-s c i a t i c 

 ligament in company 

 with the coccygeal 

 branch of the sciatic 

 artery and winds 

 around the lower bor- 

 der of, or in rare in- 

 stances pierces, the 

 gluteus m a x i m u s . 

 Perforating the deep 

 fascia slightly lateral 

 to the coccyx, it be- 

 comes superficial and 

 is distributed to the 

 integument over the 

 inner and lower por- 

 tion of the gluteus 

 maximus. 



fibres to the 



From lateral cutane- 

 ous br. of X 11. thoracic 

 From I. litmbar 

 n erve 



A gluteal cuta- 

 neous br. of small 

 sciatic nerve 



From lateral cuta- 

 neous br. of XII. 

 thoracic 



From ext. cutaneous 

 nerve 



An ext. femoral br. 

 of small sciatic 



From ext. cuta- 

 neous nerve 



of right buttock and thigh, showing cutaneous 

 nerves of posterior surface. 



Superficial dissection 

 Variations. — I n - 

 stead of piercing the 



ligament it may accompany the pudic nerve or pass between the ligament and the gluteus 

 maximus. It may be replaced by a branch of the small sciatic or by a nerve, called by Eisler 



