THE SACRAL NERVES. 



1283 



(Fig. 1084). From this structure branches pass laterally till they reach the inter- 

 val between the great sacro-sciatic ligament, which they pierce, and the deep surface 

 of the gluteus maximus, where they form a second series of loops. From the pri- 

 mary loops branches are supplied to the multifidus spinae and from the secondary 

 loops proceed two or more filaments, usually two (nn. clunium medii), which pierce 

 the gluteus maximus on a line connecting the posterior superior spine of the ilium 



Fig. 1084. 



Loops of 

 communication 

 between V. lumbar, 

 and I., II. and III. 

 posterior sacral 

 nerveS' 

 Cutaneous branches from 

 last lumbar and first 

 three sacral nerves 

 post, divisi* ns 



From XII 

 thoracic nerve 



Part of 



gluteus 



maximus, 



reflected 



of multifidus spinae muscle 



lumbar nerve, posterior division 

 I. sacral nerve, posterior division 

 II. sacral nei*ve, posterior division 



III. sacral nerve, posterior division 

 IV. sacral nerve, posterior 

 division 



Coccygeal nerve, anterior division 



V. sacral nerve, posterior division 

 Coccygeal nerve, posterior 

 division 



IV. sacral nerve, anterior 

 division, the coccygeus 

 muscle being partly cut away 



V. sacral nerve, anterior 



division 



Coccygeus muscle, 

 part of its 

 coccygeal 

 attachment cut 



Cutaneous branch 

 of IV. anterior 

 sacral nerve, giving oH 

 here also muscular 

 branches to 

 levator ani 



Dissection showing left posterior sacral ple.xus. 



and the tip of the coccyx. One is usually situated near the lower portion of the 

 sacrum and the other at the side of the coccyx. They pass laterally and supply the 

 skin of the buttock (Fig. 1083). 



The internal Ijranches (rr. mediales) of the first, second and third sacral 

 nerves are small in size and are distributed to the multifidus spinae. 



The posterior primary divisions of the fourth and fifth sacral nerves are of small 

 size. They pass below the multifidus spinse and continue as single trunks, not 

 breaking up as do the others, into two branches. They are connected with each 

 other and with the coccygeal nerve by loops which form the posterior sacro- 

 coccygeal nerve. From this structure fibres which pierce the great sacro-sciatic 

 ligament are given off to be distributed to the integument in the coccygeal region 

 (Fig. 1084). 



