SACRAL NERVES. 



537 



common branching into inner and outer pieces, like the other 

 spinal nerves ; but the last two 

 are undivided. 



The first three nerves (1 S, 2s 

 and 3 s) are covered by the 

 multifidus spinae, and divide 

 regularly. 



The inner pieces ( x ) are distri- 

 buted to the multifidus ; the last 

 of this set is very fine. 



The outer pieces ( 2 ) are larger, 

 and have communicating offsets 

 from one to another on the back 

 of the sacrum ; the branch of the 

 first is also connected with the cor- 

 responding part of the last lum- 

 bar nerve ; and the branch of the 

 third joins in a similar way the 

 sacral nerve next below. After 

 this looping they pass outwards 

 to the surface of the great 

 sacro-sciatic ligament, where they 

 join a second time, and become 

 cutaneous. 



Last two nerves (4 s and 5 s). 

 These nerves, which are below 

 the multifidus, are much smaller 

 than the preceding, and want the 

 regular branching of the others: 

 they are connected with each 

 other and the coccygeal nerve 

 by loops on the back of the 

 sacrum. A few filaments are 

 distributed over the back of the 

 coccyx. 



COCCYGEAL SERVE (1 c). Its 

 posterior primary branch issues 

 through the lower aperture of the 

 spinal canal, and appears by the 

 side of the coccyx. It is joined 

 in a loop with the last sacral 

 nerve, and ends on the posterior 

 surface of the coccyx. 



SACRAL ARTERIES. Small 

 branches of the lateral sacral 

 arteries leave the spinal canal 

 with the sacral nerves : thev 



First three 

 have 



inner and 



outer 

 branches ; 



latter give 

 cutaneous 

 offsets. 



FIG. 193. DISSECTION OF THE POS- 

 TERIOR DIVISIONS OP THE SACRAL 

 XKRVKS. 



Muscles : 



A. Multifidus spinae, and B. Erector 

 spinae : both cut. 



c. Glutens maximus detached from 

 its origin, and thrown down. 



D. Great sacro-sciatic ligament. 



Werves ; 



51. Last lumbar. 



1 s to 5 s. The five sacral nerves 

 issuing from the sacrum. 



1 c. The coccygeal nerve escaping 

 by the opening of the sacral canal. 



1. Internal offsets of the last 

 lumbar and first three sacral (these 

 are represented too large). 



2. External offsets of the same 

 nerves. 



3. Anterior, and 4, 

 primary branch of the 

 nerve. 



5. The nerve derived from the an- 

 terior divisions of the last two sacral 

 and the coccygeal nerves, piercing 

 the great sacro-sciatic ligament and 

 the gluteus maximus muscle. 



Last two are 

 undivided. 



Coccygeal 

 nerve. 



posterior 

 coccygeal 



Small sacral 

 arteries. 



supply the multifidus spinse, and 



anastomose on the back of the sacrum with offsets from the gluteal 



and sciatic arteries 



