THE PUDENDAL PLEXUS. 



1347 



posterior portion of the external sphincter and distributes sensory fibres to the 



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 mus- 

 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 jiound 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 

 pudic 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. 





Cutaneous brs. from 

 post, sacral nerves 



Inf. pudendal 



nerve, and a glu- 



teal cutaneous br. 



of small sciatic 



Small sciatic nerve 



From lateral cutane- 

 ous br. of XI I. thoracic 

 From I. lumbar 

 nerve 



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 



Superficial dissection of right buttock and thigh, showing cutaneous 

 nerves of posterior surface. 



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 



